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The Relationship between Chronic Pain Pattern, Interference with Life and Health-Related Quality of Life in a Nationwide Community Sample
Original Article The Relationship between Chronic Pain Pattern, Interference with Life and Health-Related Quality of Life in a Nationwide Community Sample ---
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From the *Faculty of Nursing, University of Iceland, Reykjavik; † Centre of Public Health Sciences, School of Health Sciences, University of Iceland, Reykjavik; ‡Faculty of Nursing, School of Health Sciences, University of Akureyri, Akureyri; § Landspitali, The National University Hospital of Iceland, Reykjavik, Iceland. Address correspondence to Thorbjorg Jonsdottir, MS, RN, University of Akureyri, School of Health Sciences, Faculty of Nursing, v/Nordurslod, 600 Akureyri, Iceland. E-mail: [email protected] Received April 20, 2013; Revised July 9, 2013; Accepted July 10, 2013. This study was financially supported by the University of Akureyri Research Fund, the Icelandic Nursing Association Research Fund, and the Ingibjorg R. Magnusdottir Research Fund. 1524-9042/$36.00 Ó 2013 by the American Society for Pain Management Nursing http://dx.doi.org/10.1016/ j.pmn.2013.07.005
Thorbjorg Jonsdottir, MS, RN,*,‡ Thor Aspelund, PhD,† Helga Jonsdottir, PhD, RN,* and Sigridur Gunnarsdottir, PhD, RN*,§
ABSTRACT:
To establish the scope of the problem of chronic pain in the population, we need to extend the focus on prevalence, the most frequently studied factor. Among other important factors is the complex relationship between the temporal characteristics of pain and their impact on peoples’ lives. The purpose of the present study was to describe the characteristics of chronic pain, including pattern, severity, location, spread, and duration, in a population-based sample and to investigate the relationships between pain pattern and impact on the individual’s life measured by interference with life and health-related quality of life (HRQoL). In this cross-sectional study, a postal questionnaire measuring pain characteristics, life interference (Brief Pain Inventory), and HRQoL (Short Form 36 Health Survey), was sent to a sample of 4,500 individuals, randomly drawn from the Icelandic National Register. The total response rate was 36.9% and was significantly higher among native Icelanders (40.6%) than individuals of non-Icelandic origin (8.6%).The prevalence of chronic pain ($3 months) was 47.5% with mean duration of 9.3 years, and 31.9% reported constant pain. Participants with constant pain reported higher life interference scores and less HRQoL than participants with intermittent or periodic pain. Hierarchical stepwise regression analyses showed that pain pattern and severity accounted for 44.4% variance for life interference. The range of the variances for these variables for the five domains of HRQoL was from 7.3% (mental health) to 53.3% (bodily pain). Pain pattern and severity are the most significant predictors of the Pain Management Nursing, Vol -, No - (--), 2013: pp 1-11
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impact of chronic pain on individual’s daily life. Ó 2013 by the American Society for Pain Management Nursing Pain is an unavoidable experience in every person’s life, a necessary biological warning signal with the purpose of alerting the individual of an impending or already existing injury (Ghallagher, 1999). When pain persists over longer periods, however, it usually loses its purpose as a warning signal. It becomes not only a sensory experience but an end result of a complex process including physical and psychosocial factors that mediate its effect on the person’s health-related quality of life (HRQoL) (Baliki, Geha, Apkarian, & Chialvo, 2008; Turk & Okifuji, 1999). Many studies have been conducted on the prevalence of chronic pain (lasting for more than 3 to 6 months), showing a wide range of prevalence, depending on differences in definitions, sampling, and research methods (Breivik, Collett, Ventafridda, Cohen, & Gallacher, 2006; Takai, Yamamoto-Mitani, Okamoto, Koyama, & Honda, 2010; Turk & Okifuji, 2002; Verhaak, Kerssens, Dekker, Sorbi, & Bensing, 1998). When studying chronic pain, factors other than prevalence may be equally important to reveal the scope of the problem. Some of these factors relate to the temporal characteristics of pain, including severity, location, spread, duration, and pattern, and their impact on people’s lives (Tripp, VanDenKerkhof, & McAlister, 2006). Living everyday life with chronic pain is not only about experiencing pain on daily basis, but is also about managing the pain in the context of everyday activities and routines. Differentiation between the occurrence of a single pain experience and longer lasting pain conditions with a more complex nature is, therefore, one of the challenges in studying pain (Eriksen, Jensen, Sjogren, Ekholm, & Rasmussen, 2003; Turk & Okifuji, 2002). HRQoL has been described as the impact of health on people’s ability to function and the perceived wellbeing in physical, social, and psychological domains of life (Leidy, Revicki, & Geneste, 1999; Naughton & Shumaker, 2003; Nordlund, Ekberg, & Kristenson, 2005; Revicki et al., 2000), particularly the ability to participate in meaningful activities within the family, workplace, and community (Vetter, 2007). HRQoL is an important indicator of how chronic pain influences the individual’s daily life and of the effectiveness of pain treatment (Moons, Budts, & De Geest, 2006). The relationship between chronic pain and HRQoL is, however, complex and multifaceted (Niv & Kreitler, 2001). Among the characteristics of chronic pain, both severity
and number of pain locations have been found to be significant in the relationship between chronic pain and HRQoL (Jamison, Fanciullo, McHugo, & Baird, 2007; Lame, Peters, Vlaeyen, Kleef, & Patijn, 2005; Laursen, Bajaj, Olesen, Delmar, & Arendt-Nielsen, 2005). Conversely, a weak relationship has been shown between HRQoL impairment and pain severity alone (Lame et al., 2005). The spread of pain in relation to severity, however, has been shown to predict the relationship between chronic pain and HRQoL (Bergman, Jacobsson, Herrstrom, & Petersson, 2004). Compared with local and regional pain, widespread pain also is related to higher pain severity, more interference with life, and negative consequences on different domains in HRQoL (Burckhardt & Jones, 2005; Peolsson, Borsbo, & Gerdle, 2007). In the literature on the relationships between chronic pain and HRQoL, little is known about how pattern of pain (constant versus intermittent) influences these relationships. The only study to date shows the pattern of pain to be a stronger predictor of HRQoL than severity and duration among patients with pain related to chronic pancreatitis (Mullady et al., 2011). No studies have been found on this relationship among adult individuals with other kinds of chronic pain. The purpose of the present study was to describe the characteristics of chronic pain, including pattern, severity, location, spread, and duration in a large nationwide population-based sample and to investigate the relationships between the pain pattern and impact on the individual’s daily life and HRQoL.
METHODS Sample and Data Collection Procedures A sample of 4,500 individuals, aged 20-70 years, was randomly drawn from the Icelandic National Registry. The National Registry holds information about names, birth dates, and addresses of all residents of Iceland. To secure a proportional sample of men and women and people from all regions of the country, the sample was stratified in relation to gender and residence. The participants were sent an information letter and a questionnaire in which they were asked to answer questions on HRQoL and whether they had felt pain during the previous week. Participants were given two response options, either filling out the questionnaire and sending by post or logging into a website and answering online. Responders who reported pain during the previous week were asked to answer questions on duration of pain, location, severity, interference with different activities of daily life, and pattern of pain. Questionnaires were marked with an
Chronic Pain Pattern and Health-Related Quality of Life
identifying number on the back side to be able to trace response rate while still ensuring privacy. To improve response rate, individuals who did not respond within two weeks received a reminder postcard, and those who had not responded within four weeks received a new questionnaire along with an information letter. The study was approved by the Icelandic National Bioethics Committee (VSNb2011030002/03.7) and the Icelandic Data Protection Authority (S5197/2011). Completing and returning the questionnaire was considered to imply informed consent for participation in the study. Instruments This study is part of more extensive research on chronic pain and HRQoL, as well as access to and use of health care and patient-provider communication. The instruments consist of questionnaires on pain, HRQoL, access to and use of health care service both generally and in relation to pain, patient-provider communication, and sociodemographic data. Data on sociodemographic characteristics, pain measures, and HRQoL are presented in this paper. Sociodemographic Characteristics. The sociodemographic data collected were age, gender, marital status, and education. Pain Severity and Interference with Life. The Icelandic version of the Brief Pain Inventory (BPI) was used to evaluate pain severity and interference with life (Cleeland & Ryan, 1994; Gunnarsdottir, Ward, & Serlin, 2008). Participants also were asked to answer questions about the duration and location of pain. The BPI contains three questions regarding pain severity during the previous 24 hours, worst pain, least pain, and average pain. The fourth severity item measures pain at present. Participants rate their pain on a scale from 0 to 10, where 0 indicates no pain and 10 is the worst pain imaginable. Interference with life is evaluated by questions on the impact of pain on seven aspects of daily life: mood, walking ability, work, social activity, sleep, and life enjoyment. Participants rate the impact of pain on these seven items on a scale from 0 to 10, anchored with ‘‘does not interfere’’ (0) and ‘‘completely interferes’’ (10) (Cleeland & Ryan, 1994). By taking the mean of the four severity items and the seven interference items separately, two composite scores, the Pain Severity Index and the Pain Interference Index, are calculated (Zelman, Gore, Dukes, Tai, & Brandenburg, 2005). The BPI has been translated into Icelandic and validated in a general population sample of Icelandic adults experiencing pain of various origins and found to be both reliable and valid (Gunnarsdottir et al., 2008). In the present study, the internal consistency was a ¼ 0.89
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for the severity scale and a ¼ 0.91 for the interference scale. In the Icelandic version, the time reference used is the past week as opposed to the past 24 hours in the English version (Gunnarsdottir et al., 2008). Health-Related Quality of Life. The Short Form 36 Health Survey (SF-36v2) is a 36-item self-rating questionnaire developed to assess some primary aspects of HRQoL, perceived health status in various health conditions, and diseases (Beaton, Hogg-Johnson, & Bombardier, 1997; Vetter, 2007). The instrument comprises 36 multiple choice questions, and responses vary from yes or no answers to a six-point rating scale (ordinal) (Beaton et al., 1997). Questions are designed to assess eight different health domains: (1) physical functioning (PF, 10 questions); (2) role physical (RP, 4 questions); (3) bodily pain (BP, 2 questions); (4) general health (GH, 5 questions); (5) vitality (VT, 4 questions); (6) social functioning (SF, 2 questions); (7) role emotional (RE, 3 questions); and (8) mental health (MH, 5 questions). In addition, there is one single question asking respondents to compare their health now with how it was one year ago on a scale from 1-5 (Wallin & Raak, 2008; Ware, 2000). Each dimension is scored from 0 (worst) to 100 (best possible health status) (Jenkinson, Stewart-Brown, Petersen, & Paice, 1999; Ware, 2000). The eight domains are hypothesized to form two distinct higher-order clusters due to the physical and mental health variance that they have in common (Ware, 2012) The reliability and validity of the instrument in relation to different health conditions has been widely tested and confirmed (Beaton et al., 1997; Ware, 2012). In the present study the internal consistency was acceptable for all scales, with Chronbach’s alpha ranging from 0.78 (GH) to 0.94 (RP). Pattern, Location and Spread of Pain. Respondents were asked to answer a question about the pattern of pain, classified as constant pain (pain all the time), daily intermittent (daily pain with one to a few hours break during the day), frequent intermittent (pain most days but pain-free days in between), and periodic (pain-free periods for days or weeks but pain episodes in between). Location of pain was classified by asking participants to indicate all areas of the body where they sensed pain by marking them on a list of 19 areas of the body (e.g., head, neck, hand/hands, foot/feet etc.). Spread of pain was classified as number of pain locations. Statistical Analyses Data were analyzed using SPSS for Windows (version 20.0). Descriptive statistics were used to present the sample’s demographic characteristics and causes,
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duration, location, spread, pain pattern, pain severity, as well as interference with life and HRQoL in relation to pain. ANOVA and trend analyses were used to check for relationships between pain pattern, interference with life, and HRQoL. Predictors of interference with life and HRQoL (SF-36 scores) were calculated by means of a hierarchical stepwise regression analysis, in which the predictors of interest—pattern, severity, and spread of pain—were entered in steps one to three and controlled for demographic variables (gender, age, education) by entering them in the final fourth step.
RESULTS Response Rate Of the 4,500 questionnaires mailed, a total of 1,629 questionnaires were returned (37.9%). Of the returned questionnaires, 63 were incomplete and 1,586 were completed (36.9%) (Fig. 1). Of 4,500 individuals in the original sample, 564 were considered of non-Icelandic origin. Only 43 (8.6%) of these returned a filled questionnaire. The questionnaires were only in Icelandic, and although only one person reported being unable to participate because of lack of proficiency in Icelandic, it can be assumed that the low response rate in this group was probably due to language difficulties. The calculation of response rate without participants of non-Icelandic origins would have been higher (40.6%). However, in an attempt to preserve a multicultural approach, it was decided to include all in the sample. The inclusion process of participants is outlined in Figure 1. Characteristics of the Sample (n ¼ 1,586) Most respondents who returned a completed questionnaire were women (56.5%). The total sample mean age was 46.2 years (SD ¼ 13.99, range 20-70 years; women: 45.3, men: 47.3). Respondents were significantly older than nonrespondents (mean age of nonparticipants, 38.7; p < .005), and response rate was lower among younger individuals and men. Differences between age distribution of respondents and nonrespondents are listed in Table 1. Most respondents were married or cohabitating, 27.3% had less than 11 years of school education. Sociodemographic characteristics (gender, age groups, marital status, and education) are listed in Table 1. Duration and Causes of Pain From the total sample of respondents (n ¼ 1,586), 873 persons (55.0%) reported that they had felt some kind of pain (other than minor headache, sprain, toothache, or menstrual pain) during the previous week. A similar number (n ¼ 828, 52.2%) reported that they had been
diagnosed with some chronic disease or health problem, with hypertension (n ¼ 374, 23.6%) and rheumatism (n ¼ 200, 12.6%) most frequently reported. Of those who answered the question on duration of pain (n ¼ 816), most 92.4% (n ¼ 754) had pain for three months or longer. Only 62 (7.6%) reported pain for less than three months. The total prevalence of chronic pain ($3 months) was 47.5% (n ¼ 754) with mean duration of 9.3 years (median ¼ 6 years, SD ¼ 10). The prevalence of pain in relation to demographic characteristics is listed in Table 1. The most frequently reported causes of chronic pain were myalgia (n ¼ 289, 41.1%), old trauma (n ¼188, 26.7%), wear and tear (n ¼176, 25.0%), osteoarthritis (n ¼ 168, 23.9%), and fibromyalgia (n ¼ 90, 12.8%). Pain Locations and Spread The most frequently reported location of chronic pain was low back (61.5%). Other frequently reported locations were shoulders (45.6%), neck (35.7%), head (32.4%), and knee (35.7%). Few (12%) reported one location of pain. One third (30.2%) reported pain in 2-3 locations, and another third (32.1%) reported pain in 4-6 locations. Pain Severity, Duration, and Interference with Life and HRQoL The mean value for the pain severity index for participants reporting pain $3 months was 3.4 (SD ¼ 1.83) and 2.6 (SD ¼ 2.20) for the interference index. For those who reported pain <3 months, these numbers for the pain severity index were 2.4 (SD ¼1.70) and the interference index 1.6 (SD ¼ 1,69). Both indices increased with longer duration of pain, and the differences were significant between groups reporting pain for shorter or longer than three months (p < .01). There was a significant difference in all SF-36 subscales between those reporting pain during the previous week and those with no pain during the previous week (p < .01), with the former group reported higher interference with life and lower HRQoL than the latter. There was also a significant difference in the interference with life scale and in all SF-36 subscales (p < .01) between groups reporting pain for <3 months or $3 months, except for Role Emotional subscale (p ¼ .07). Table 2 shows an overview of HRQoL and interference with life in relation to pain duration. Pain Pattern, Interference with Life, and HRQoL Of those who reported pain during the previous week, almost one third (29.8%) reported the pain to be
Chronic Pain Pattern and Health-Related Quality of Life
FIGURE 1.
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Flow chart of study participants.
constant and one fifth (22.5%) reported periodic pain with pain-free days or weeks in between. One third (31.9%) of those reporting pain for $3 months reported constant pain and only 18.9% reported pain to be periodic. Among those reporting pain for less than 3 months, periodic (52.5%) and frequent intermittent (22%) were the most common pain patterns. Patterns of chronic pain in relation to demographic information (gender and education) are listed in Table 3. The relationships between different patterns and interference with life as well as HRQoL subdomains are shown in Table 4. As shown in Table 4, participants reporting constant pain had the highest values in
interference with life and lowest values in all HRQoL subdomains. Prediction of Interference with Life and Domains of HRQoL Tables 5 and 6 summarize hierarchical regression models showing the predictors that were included in the stepwise regression analyses. In the first step, pattern variables (constant, daily intermittent, and frequent intermittent versus periodical pain) were entered. All patterns were significantly related to interference with life and all domains of HRQoL. However, the strength of this relationship was different in different domains, being higher in the physical domains
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TABLE 1. Demographic Information for Respondents and Nonrespondents
Gender Female Male Age groups 20-30 31-40 41-50 51-60 61-70 Marrital status Married/cohabit Single Divorced Widowed Education Lower secondary school (#10 years) Upper secondary school general (>10 years) Upper secondary school occupational (>10 years) University #4 years University >4 years
Respondents Completed Lists (%)
Non respondents (%)
Total in Sample
Pain Last Week (%)
Pain $3 Months (%)
875 (40.7) 673 (30.0)
1273 (59.3) 1569 (70.0)
2148 2242
501 (57.3) 358 (53.2)
435 (49.7) 307 (45.6)
274 (21.8) 270 (26.3) 355 (40.7) 345 (44.1) 303 (54.1)
984 (78.2) 757 (73.7) 518 (59.3) 437 (55.9) 257 (45.9)
1258 1027 873 782 560
138 (50.4) 140(51.9) 204 (57.5) 198 (57.4) 179 (59.1)
114 (41.6) 123 (45.6) 169 (47.6) 179 (51.9) 157 (51.8)
1139 (73.7) 281 (18.2) 98 (6.3) 28 (1.8)
647 (56.8) 142 (50.5) 53 (54.1) 16 (57.1)
556 (48.8) 128 (45.6) 43 (43.9) 15 (53.6)
417 (27.3)
254 (60.9)
222 (53.2)
191 (12.5)
100 (52.4)
83 (43.5)
432 (28.3)
258 (59.7)
219 (50.7)
298 (19.5) 191 (12.5)
159 (53.4) 80 (41.9)
147 (49.3) 63 (33.0)
(PF, RP, BP, and GH) compared with the mental domains (VT, SF,RE, and MH). The coefficient for variance of pain pattern alone, in relation to interference with life and different HRQoL domains was lowest in MH (R2 ¼ .035) and RE (R2 ¼ .054) and highest in BP (R2 ¼ .296) and RP (R2 ¼ .147) (Table 6). Steps 2 and 3 show the additional variance explained by pain severity and spread. As shown in
Table 5, severity turned out to be the most important factor for interference with life. Pattern alone explained 18.3% of variance; pain pattern and pain severity explained 44.4%, and after adding spread of pain, the variance explained was 45.2%. Severity was also the strongest predictor in most HRQoL domains, which can be seen in the change in R2 between step 2 and 3 in Table 6. Spread of pain did not add much
TABLE 2. Pain Duration Versus Interference with Life and HRQoL (SF-36 Scores) Duration of pain Variable
Total Score Mean (SD)
No Pain Previous Week
Pain Previous Week
Pain <3 Months
Pain $3 Months
Interference with life Physical functioning Role physical Bodily pain General health Vitality Social functioning Role emotional Mental health
2.46 (2.17) 84.65 (22.29) 78.87 (26.36) 68.84 (25.63) 69.39 (21.45) 57.67 (20.72) 81.62 (22.69) 84.03 (23.09) 75.53 (17.85)
— 92.81 (16.32) 89.53 (17.47) 85.53 (17.47) 77.45 (17.37) 64.78 (18.25) 87.61 (18.46) 8854 (19.78) 78.68 (15.88)
2.54 (2.18) 79.54 (23.57) 71.19 (28.93) 56.87 (24.14) 64.34 (22.33) 52.90 (20.81) 77.40 (24.37) 81.34 (24.19) 73.29 (18.97)
1.62 (1.70) 89.30 (17.5) 84.02 (20.74) 69.72 (20.88) 73.91 (19.45) 61.67 (18.81) 86.42 (18.77) 87.89 (20.31) 77.93 (13.44)
2.63 (2.20) 78.37 (24.00) 69.75 (29.51) 55.41 (24.29) 63.21 (22.50) 51.79 (2098) 76.53 (24.77) 80.62 (2435) 72.88 (13.44)
Note. Interference with life is measured on a 0-10 scale. HRQoL (SF-36 scales) is measured on a 0-100 scale.
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Chronic Pain Pattern and Health-Related Quality of Life
TABLE 3. Pattern of Chronic Pain Pain Pattern ($3months) Variable
Constant Pain (%)
Daily Intermittent (%)
Frequent Intermittent (%)
Periodal (%)
Pain $3 months (n ¼ 705) Gender (n ¼ 753) Men (n ¼ 311) Women (n ¼ 442) Education (n ¼ 745) Lower secondary school (#10 years) Upper secondary school general (>10 years) Upper secondary school occupational (>10 years) University #4 years University >4 years
225 (31.9)
151 (21.4)
196 (27.8)
133 (18.9)
83 (29.3) 140 (34.0)
55 (19.4) 93 (22.6)
82 (29.0) 110 (26.7)
63 (22.3) 69 (16.7)
83 (40.9)
46 (22.7)
47 (23.2)
27 (13.3)
25 (32.9)
15 (19.7)
18 (23.7)
18 (23.7)
60 (29.3)
44 (21.5)
59 (28.8)
42 (20.5)
37 (25.5) 16 (27.6)
31 (21.4) 10 (17.2)
53 (36.6) 15 (25.9)
24 (16.6) 17 (29.3)
to the variance explained, except for the VT and RE domains, in which spread was a stronger predictor than severity. In step 4, demographic variables (gender, age, education) were entered. None of these variables had a significant influence on the relationship between interference with life and any of the research variables (pattern, severity, spread). Gender was not significantly related to any of the HRQoL domains. Age was significantly related to PF, VT, and MH, although the relationship was weak. Education was not significantly related to any domains except PF and RE. Although the pain pattern was a significant predictor for the relationship between chronic pain and interference with life as well as in all HRQoL domains, this became mostly nonsignificant when pain severity was added to the regression model in step 2. Severity was significantly related to both interference with life score and all HRQoL domains. Spread of pain added little to the variance of research variables, except for the VT and RE domains. Severity was the strongest predictor in most domains, as seen in the change in R2 between steps 1 and 2.
DISCUSSION The aim of the present study was to describe the characteristics of chronic pain, including pattern, severity, location, spread, and duration in a nationwide population-based sample and to investigate the relationships between pain pattern and impact on the individual’s life as measured by interference with life and HRQoL. This study is the first to measure the
characteristics of chronic pain in a large sample of the Icelandic general population. This is also the first population-based study investigating the impact of pain pattern on the relationship between chronic pain and interference with life and HRQoL. Prior work on the relationship between chronic pain and HRQoL has documented the importance of pain severity and spread in the relationship between chronic pain and HRQoL (Bergman et al., 2004; Jamison et al., 2007; Lame et al., 2005; Laursen et al., 2005). In some studies, however, pain severity alone has, been shown to be a weak predictor in the relationship between pain and HRQoL (Lame et al., 2005) and significant only if in relation to spread (Bergman et al., 2004). In the present study, the interplay between pain severity and number of pain locations as predictors for the relationship between chronic pain and HRQoL was different from what has been reported in earlier studies. The fact that earlier studies have not considered the influence of pain pattern in this relationship might be the explanation for this difference. When pain severity was added to the regression model, there was a significant increase in variance both in the interference scale as well as in all domains of HRQoL, indicating that pain severity in relation to pain pattern significantly predicts the relationship between chronic pain and its influence on the individual’s life. Finally, when the number of pain locations was added to the regression model, the difference in variance was much less than for pain severity, although significant. In the present study, more than half of respondents reporting chronic pain ($3 months) had constant or
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TABLE 4. Scores of Interference and SF-36 Scales in Relation to Pain Pattern. ANOVA and Linear Trend Analyses Variable Interference with life Constant pain (n ¼ 187) Daily intermittent (n ¼ 138) Frequent intermittent (n ¼ 179) Periodal (n ¼ 117) Physical Functioning Constant pain (n ¼ 223) Daily intermittent (n ¼ 148) Frequent intermittent (n ¼ 194) Periodal (n ¼ 133) Role Physical Constant pain (n ¼ 221) Daily intermittent (n ¼ 149) Frequent intermittent (n ¼ 192) Periodal (n ¼ 132) Bodily Pain Constant pain (n ¼ 225) Daily intermittent (n ¼ 148) Frequent intermittent (n ¼ 194) Periodal (n ¼ 132) General Health Constant pain (n ¼ 225) Daily intermittent (n ¼ 151) Frequent intermittent (n ¼ 196) Periodal (n ¼ 133) Vitality Constant pain (n ¼ 224) Daily intermittent (n ¼ 149) Frequent intermittent (n ¼ 194) Periodal (n ¼ 132) Social Functioning Constant pain (n ¼ 225) Daily intermittent (n ¼ 149) Frequent intermittent (n ¼ 194) Periodal (n ¼ 132) Role Emotional Constant pain (n ¼ 220) Daily intermittent (n ¼ 147) Frequent intermittent (n ¼ 191) Periodal (n ¼ 131) Mental Health Constant pain (n ¼ 224) Daily intermittent (n ¼ 148) Frequent intermittent (n ¼ 194) Periodal (n ¼ 132)
Mean Score
SD
3.75 3.05 1.99 1.23
2.46 2.00 1.78 1.30
67.56 74.83 86.34 87.44
26.98 22.65 15.99 19.83
57.28 61.65 78.45 84.67
30.55 30.65 24.36 20.50
40.57 46.34 64.16 72.79
23.19 20.33 15.96 18.47
55.88 58.63 67.83 72.03
24.20 21.14 20.14 17.92
43.47 49.45 55.28 61.04
21.21 20.12 19.67 17.04
68.28 76.26 79.45 84.75
27.92 23.95 21.64 18.49
72.58 80.41 83.27 88.00
29.49 24.42 20.49 17.02
68.12 74.49 73.06 77.96
21.21 18.55 18.08 15.65
Linear Trend p Value <.001
<.001
<.001
<.001
<.001
<.001
<.001
<.001
<.001
Note: Interference with life is measured on a 0-10 scale. HRQoL (SF-36 scales) is measured on a 0-100 scale.
daily pain. This is similar to results from a large population-based study on the prevalence and characteristics of chronic pain in 15 European countries and Israel, in which approximately half of the participants reporting chronic pain ($6 months) had constant pain (Breivik et al., 2006). The results show that pain pattern is an important factor in the relationship between chronic pain and interference with life as well as all domains of HRQoL. This accounts for both
physical and psychosocial domains, even when controlled for gender, age, and education, and these influences are stronger the more constant the pain is. Constant and daily pain significantly influences the relationship in interference with life as well as in all HRQoL domains. Frequent intermittent or periodic pain has less influence, but also significant, in the interference with life scale as well as the bodily pain, vitality, and mental health HRQoL scales.
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Chronic Pain Pattern and Health-Related Quality of Life
TABLE 5. Summary of the Hierarchical Regression Analyses for Interference with Life Model 1 Variable
p
B
Interference with life, N ¼ 620 Constant Pain pattern Constant pain vs. Periodical Daily intermittent vs. Periodical Frequent intermittent vs. Periodical Severity Spread Gender Age Education U secondary vs. L secondary U occupational vs. L secondary University <4 vs. L secondary University >4 vs. L Secondary R2 p value for change in R2
Model 2 p
B .271
1.267 2.447 1.806 .711
Model 3
<.001 <.001 .003
.183 <.001
Model 4 p
B .391
p
B .221
.550 .550 .291
.013 .013 .144
.470 .497 .296
.035 .025 .134
.448 .510 .303
.044 .022 .126
.733
<.001
.689 .062
<.001 .003
.698 .064 .178 .005
<.001 .003 .199 .379
.250 .362 .102 .120
.317 .037 .603 .649
.444 <.001
.452 .003
.459 .240
Note: Interference with life is measured on a 0-10 scale.
This study shows that pain pattern and pain severity are significant predictors for the impact of chronic pain on an individual’s daily life. As pain becomes more constant and pain severity increases, there are more detrimental influences. Pain pattern in relation to pain severity accounts for as great as a 44.4% variance for interference with life, and the number of pain locations adds very little to this relationship. Pain pattern and pain severity account for 20.4%-53.3% of variance in physical domains of HRQoL (PF, RP, BP, and GH). In the four psychosocial domains (VT, SF, RE, and MH), pattern, severity and spread account for less variance in the relationship between pain and HRQoL than in the physical domains. In the SF and MH domains,
pattern and severity account for 16.5% and 7.3% of variance, respectively. The two other psychosocial domains, VT and RE, are the only domains of HRQoL in which spread of pain is a more important indicator than severity. In these two domains, pattern and spread account for 17.6% and 10.6% of variance, respectively. In the present study, pain pattern and severity had a stronger relationship with the physical domains of HRQoL than the mental domains. On the other hand, pain spread is a more important factor than severity in the relationship between chronic pain and at least some of the mental domains. Similar results regarding the importance of pain spread in the relationship
TABLE 6. Summary of the Hierarchical Regression Analyses for SF-36 Scales R2/p Value for Change in R2 (N ¼ 674) Evaluation Criteria
Model 1
Model 2
Model 3
Model 4
Physical Functioning Role Physical Bodily Pain General Health Vitality Social Functioning Role Emotional Mental Health
.132/<.001 .147/<.001 .296/<.001 .085/<.001 .099/<.001 .061/<.001 .054/<.001 .035/<.001
.279/<.001 .323/<.001 .533/<.001 .204/<.001 .176/<.001 .165/<.001 .106/<.001 .073/<.001
.301/<.001 .351/<.001 .543/<.001 .243/<.001 .214/<.001 .185/<.001 .127/<.001 .090/.001
.328/<.001 .354/.756 .545/.791 .259/.028 .257/<.001 .201/.047 .159/<.001 .150/<.001
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Jonsdottir et al.
between chronic pain and the mental components of HRQoL, especially, were reported by Bergman et al., 2004. This might indicate that pain characteristics (e.g., severity and spread) influence physical and mental components of each individual’s life differently. The results of the present study indicate that pain pattern is an important factor in how chronic pain influences the individual’s daily life—the more constant the pain, the more detrimental the effects. It also is important to notice that more than half (53.3%) of participants experiencing chronic pain had constant or at least daily pain and that most individuals with pain duration less than 3 months reported periodic pain. This indicates that as pain is prolonged, the risk for constant or daily pain increases. This is important to notice in the clinical practice. When the patient seeks care for pain, it is necessary to approach pain in a broad spectrum and consider different characteristics and its effects on daily life. This is important to prevent pain from becoming chronic, constant, or daily in pattern. Earlier studies also have suggested the urgency of a preventive perspective in the clinical assessment of prolonged pain (Bergman et al., 2004; Peolsson et al., 2007). There are a number of limitations to the present study that should be taken into account. The crosssectional design of this study makes causal inferences impossible. The major limitation is the relatively low response rate despite careful attention given in the study design to maximizing the number of responses. It was possible to compare responders and nonresponders in terms of age and gender, and a significant difference between those who responded and those who did not was found. The response rate was 40.7% among women and 30.0% among men, and the responders were significantly older than nonresponders, with a 21.8% response rate in the youngest age group (20-30 years) and 54.1% in the oldest group (61-70 years). Prior studies on the prevalence of pain have shown a similar pattern (Rustoen et al., 2004). It is also worth noting that most respondents reporting pain had felt pain for three months or longer, making the prevalence of chronic pain relatively high compared with the occurrence of pain of shorter duration. Based on this, it can be speculated whether those who
were invited to participate were more likely to do so if they felt pain and had done so for a long time and, therefore, felt that they had some investment in the topic. Another important issue in relation to the low response rate is that, among the total of 4,500 individuals, 564 were considered to be of non-Icelandic origin. Among these individuals, the response rate was much lower than in the total sample, indicating that the reason for the relatively low total response rate might in part be language difficulties. This study is the first general population-based study investigating the impact of pain pattern on the relationship between chronic pain and interference with life and HRQoL. It is also the first to evaluate the characteristics of chronic pain in a large sample in the Icelandic general population. It thereby contributes valuable knowledge on the impact of pattern of chronic pain on individuals’ daily lives and HRQoL in a large population-based sample.
CONCLUSIONS This study found a significant impact of pain pattern on the relationship between chronic pain and interference with life and different domains of HRQoL and how pain severity adds to this relationship. This is important to notice in the clinical practice related to individuals with chronic pain and to approach pain in a broad spectrum and consider different characteristics of pain and its effect on the individual’s different aspects of life. Further studies should be carried out investigating the relationship between pain and interference with life and HRQoL among individuals experiencing chronic pain. For example, a longitudinal study might be conducted on changes in pain pattern over time and how these changes influence the impact of pain on an individual’s life over time. A qualitative approach in which individuals experiencing chronic pain were asked to describe the pattern of their pain and how it influences their daily life activities in their own words would deepen the knowledge in this area. Acknowledgments We are grateful to all those who participated in this study.
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Bergman, S., Jacobsson, L. T., Herrstrom, P., & Petersson, I. F. (2004). Health status as measured by SF-36 reflects changes and predicts outcome in chronic musculoskeletal pain: A 3-year follow up study in the general population. Pain, 108(1-2), 115–123. Breivik, H., Collett, B., Ventafridda, V., Cohen, R., & Gallacher, D. (2006). Survey of chronic pain in Europe: Prevalence, impact on daily life, and treatment. European Journal of Pain (London, England), 10(4), 287–333. Burckhardt, C. S., & Jones, K. D. (2005). Effects of chronic widespread pain on the health status and quality of life of women after breast cancer surgery. Health and Quality of Life Outcomes, 3, 30. Cleeland, C. S., & Ryan, K. M. (1994). Pain assessment: Global use of the brief pain inventory. Annals of the Academy of Medicine, Singapore, 23(2), 129–138. Eriksen, J., Jensen, M. K., Sjogren, P., Ekholm, O., & Rasmussen, N. K. (2003). Epidemiology of chronic nonmalignant pain in denmark. Pain, 106(3), 221–228. Ghallagher, R. M. (1999). Primary care and pain medicine. A community solution to the public health problem of chronic pain. The Medical Clinics of North America, 83(3), 555–583. Gunnarsdottir, S., Ward, S., & Serlin, R. C. (2008). Attitudinal barriers to cancer pain management in the Icelandic population. Cancer Nursing, 31(2), 95–102. Jamison, R. N., Fanciullo, G. J., McHugo, G. J., & Baird, J. C. (2007). Validation of the short-form interactive computerized quality of life scale (ICQOL-SF). Pain Medicine (Malden, Mass.), 8(3), 243–250. Jenkinson, C., Stewart-Brown, S., Petersen, S., & Paice, C. (1999). Assessment of the SF-36 version 2 in the United Kingdom. Journal of Epidemiology and Community Health, 53(1), 46–50. Lame, I. E., Peters, M. L., Vlaeyen, J. W., Kleef, M., & Patijn, J. (2005). Quality of life in chronic pain is more associated with beliefs about pain, than with pain intensity. European Journal of Pain (London, England), 9(1), 15–24. Laursen, B. S., Bajaj, P., Olesen, A. S., Delmar, C., & ArendtNielsen, L. (2005). Health related quality of life and quantitative pain measurement in females with chronic non-malignant pain. European Journal of Pain (London, England), 9(3), 267–275. Leidy, N. K., Revicki, D. A., & Geneste, B. (1999). Recommendations for evaluating the validity of quality of life claims for labeling and promotion. Value in Health: The Journal of the International Society for Pharmacoeconomics and Outcomes Research, 2(2), 113–127. Moons, P., Budts, W., & De Geest, S. (2006). Critique on the conceptualisation of quality of life: A review and evaluation of different conceptual approaches. International Journal of Nursing Studies, 43(7), 891–901. Mullady, D. K., Yadav, D., Amann, S. T., O’Connell, M. R., Barmada, M. M., Elta, G. H., Scheiman, J. M., Wamsteker, E. J., Chey, W. D., Korneffel, M. L., Weinman, B. M., Slivka, A., Sherman, S., Hawes, R. H., Brand, R. E., Burton, F. R., Lewis, M. D., Gardner, T. B., Gelrud, A., DiSario, J., Baillie, J., Banks, P. A., Whitcomb, D. C., Anderson, M. A., & NAPS2 Consortium (2011). Type of pain, pain-associated complications, quality of life, disability and resource utilisation in chronic pancreatitis: A prospective cohort study. Gut, 60(1), 77–84. Naughton, M. J., & Shumaker, S. A. (2003). The case for domains of function in quality of life assessment. Quality of Life Research: An International Journal of Quality of Life Aspects of Treatment, Care and Rehabilitation, 12(Suppl 1), 73–80.
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Niv, D., & Kreitler, S. (2001). Pain and quality of life. Pain Practice: The Official Journal of World Institute of Pain, 1(2), 150–161. Nordlund, A., Ekberg, K., & Kristenson, M. (2005). EQ-5D in a general population survey–a description of the most commonly reported EQ-5D health states using the SF-36. Quality of Life Research: An International Journal of Quality of Life Aspects of Treatment, Care and Rehabilitation, 14(4), 1099–1109. Peolsson, M., Borsbo, B., & Gerdle, B. (2007). Generalized pain is associated with more negative consequences than local or regional pain: A study of chronic whiplash-associated disorders. Journal of Rehabilitation Medicine: Official Journal of the UEMS European Board of Physical and Rehabilitation Medicine, 39(3), 260–268. Revicki, D. A., Osoba, D., Fairclough, D., Barofsky, I., Berzon, R., Leidy, N. K., & Rothman, M. (2000). Recommendations on health-related quality of life research to support labeling and promotional claims in the united states. Quality of Life Research: An International Journal of Quality of Life Aspects of Treatment, Care and Rehabilitation, 9(8), 887–900. Rustoen, T., Wahl, A. K., Hanestad, B. R., Lerdal, A., Paul, S., & Miaskowski, C. (2004). Prevalence and characteristics of chronic pain in the general Norwegian population. European Journal of Pain (London, England), 8(6), 555–565. Takai, Y., Yamamoto-Mitani, N., Okamoto, Y., Koyama, K., & Honda, A. (2010). Literature review of pain prevalence among older residents of nursing homes. Pain Management Nursing: Official Journal of the American Society of Pain Management Nurses, 11(4), 209–223. Tripp, D. A., VanDenKerkhof, E. G., & McAlister, M. (2006). Prevalence and determinants of pain and painrelated disability in urban and rural settings in southeastern ontario. Pain Research & Management: The Journal of the Canadian Pain Society ¼ Journal De La Societe Canadienne Pour Le Traitement De La Douleur, 11(4), 225–233. Turk, D. C., & Okifuji, A. (1999). Assessment of patients’ reporting of pain: An integrated perspective. Lancet, 353(9166), 1784–1788. Turk, D. C., & Okifuji, A. (2002). Psychological factors in chronic pain: Evolution and revolution. Journal of Consulting and Clinical Psychology, 70(3), 678–690. Verhaak, P. F., Kerssens, J. J., Dekker, J., Sorbi, M. J., & Bensing, J. M. (1998). Prevalence of chronic benign pain disorder among adults: A review of the literature. Pain, 77(3), 231–239. Vetter, T. R. (2007). A primer on health-related quality of life in chronic pain medicine. Anesthesia and Analgesia, 104(3), 703–718. Wallin, M. K., & Raak, R. I. (2008). Quality of life in subgroups of individuals with whiplash associated disorders. European Journal of Pain (London, England), 12(7), 842–849. Ware J. E. Jr. (2000). SF-36 health survey update. Spine, 25(24), 3130–3139. Ware, J. E., Jr. (2012). SF-36Ò health survey update. Retrieved November 11, 2012 from http://www.sf-36.org/ tools/SF36.shtml#TRANS Zelman, D. C., Gore, M., Dukes, E., Tai, K. S., & Brandenburg, N. (2005). Validation of a modified version of the brief pain inventory for painful diabetic peripheral neuropathy. Journal of Vascular Nursing: Official Publication of the Society for Peripheral Vascular Nursing, 23(3), 97–104.
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From the *Faculty of Nursing, University of Iceland, Reykjavik; † Centre of Public Health Sciences, School of Health Sciences, University of Iceland, Reykjavik; ‡Faculty of Nursing, School of Health Sciences, University of Akureyri, Akureyri; § Landspitali, The National University Hospital of Iceland, Reykjavik, Iceland. Address correspondence to Thorbjorg Jonsdottir, MS, RN, University of Akureyri, School of Health Sciences, Faculty of Nursing, v/Nordurslod, 600 Akureyri, Iceland. E-mail: [email protected] Received April 20, 2013; Revised July 9, 2013; Accepted July 10, 2013. This study was financially supported by the University of Akureyri Research Fund, the Icelandic Nursing Association Research Fund, and the Ingibjorg R. Magnusdottir Research Fund. 1524-9042/$36.00 Ó 2013 by the American Society for Pain Management Nursing http://dx.doi.org/10.1016/ j.pmn.2013.07.005
Thorbjorg Jonsdottir, MS, RN,*,‡ Thor Aspelund, PhD,† Helga Jonsdottir, PhD, RN,* and Sigridur Gunnarsdottir, PhD, RN*,§
ABSTRACT:
To establish the scope of the problem of chronic pain in the population, we need to extend the focus on prevalence, the most frequently studied factor. Among other important factors is the complex relationship between the temporal characteristics of pain and their impact on peoples’ lives. The purpose of the present study was to describe the characteristics of chronic pain, including pattern, severity, location, spread, and duration, in a population-based sample and to investigate the relationships between pain pattern and impact on the individual’s life measured by interference with life and health-related quality of life (HRQoL). In this cross-sectional study, a postal questionnaire measuring pain characteristics, life interference (Brief Pain Inventory), and HRQoL (Short Form 36 Health Survey), was sent to a sample of 4,500 individuals, randomly drawn from the Icelandic National Register. The total response rate was 36.9% and was significantly higher among native Icelanders (40.6%) than individuals of non-Icelandic origin (8.6%).The prevalence of chronic pain ($3 months) was 47.5% with mean duration of 9.3 years, and 31.9% reported constant pain. Participants with constant pain reported higher life interference scores and less HRQoL than participants with intermittent or periodic pain. Hierarchical stepwise regression analyses showed that pain pattern and severity accounted for 44.4% variance for life interference. The range of the variances for these variables for the five domains of HRQoL was from 7.3% (mental health) to 53.3% (bodily pain). Pain pattern and severity are the most significant predictors of the Pain Management Nursing, Vol -, No - (--), 2013: pp 1-11
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impact of chronic pain on individual’s daily life. Ó 2013 by the American Society for Pain Management Nursing Pain is an unavoidable experience in every person’s life, a necessary biological warning signal with the purpose of alerting the individual of an impending or already existing injury (Ghallagher, 1999). When pain persists over longer periods, however, it usually loses its purpose as a warning signal. It becomes not only a sensory experience but an end result of a complex process including physical and psychosocial factors that mediate its effect on the person’s health-related quality of life (HRQoL) (Baliki, Geha, Apkarian, & Chialvo, 2008; Turk & Okifuji, 1999). Many studies have been conducted on the prevalence of chronic pain (lasting for more than 3 to 6 months), showing a wide range of prevalence, depending on differences in definitions, sampling, and research methods (Breivik, Collett, Ventafridda, Cohen, & Gallacher, 2006; Takai, Yamamoto-Mitani, Okamoto, Koyama, & Honda, 2010; Turk & Okifuji, 2002; Verhaak, Kerssens, Dekker, Sorbi, & Bensing, 1998). When studying chronic pain, factors other than prevalence may be equally important to reveal the scope of the problem. Some of these factors relate to the temporal characteristics of pain, including severity, location, spread, duration, and pattern, and their impact on people’s lives (Tripp, VanDenKerkhof, & McAlister, 2006). Living everyday life with chronic pain is not only about experiencing pain on daily basis, but is also about managing the pain in the context of everyday activities and routines. Differentiation between the occurrence of a single pain experience and longer lasting pain conditions with a more complex nature is, therefore, one of the challenges in studying pain (Eriksen, Jensen, Sjogren, Ekholm, & Rasmussen, 2003; Turk & Okifuji, 2002). HRQoL has been described as the impact of health on people’s ability to function and the perceived wellbeing in physical, social, and psychological domains of life (Leidy, Revicki, & Geneste, 1999; Naughton & Shumaker, 2003; Nordlund, Ekberg, & Kristenson, 2005; Revicki et al., 2000), particularly the ability to participate in meaningful activities within the family, workplace, and community (Vetter, 2007). HRQoL is an important indicator of how chronic pain influences the individual’s daily life and of the effectiveness of pain treatment (Moons, Budts, & De Geest, 2006). The relationship between chronic pain and HRQoL is, however, complex and multifaceted (Niv & Kreitler, 2001). Among the characteristics of chronic pain, both severity
and number of pain locations have been found to be significant in the relationship between chronic pain and HRQoL (Jamison, Fanciullo, McHugo, & Baird, 2007; Lame, Peters, Vlaeyen, Kleef, & Patijn, 2005; Laursen, Bajaj, Olesen, Delmar, & Arendt-Nielsen, 2005). Conversely, a weak relationship has been shown between HRQoL impairment and pain severity alone (Lame et al., 2005). The spread of pain in relation to severity, however, has been shown to predict the relationship between chronic pain and HRQoL (Bergman, Jacobsson, Herrstrom, & Petersson, 2004). Compared with local and regional pain, widespread pain also is related to higher pain severity, more interference with life, and negative consequences on different domains in HRQoL (Burckhardt & Jones, 2005; Peolsson, Borsbo, & Gerdle, 2007). In the literature on the relationships between chronic pain and HRQoL, little is known about how pattern of pain (constant versus intermittent) influences these relationships. The only study to date shows the pattern of pain to be a stronger predictor of HRQoL than severity and duration among patients with pain related to chronic pancreatitis (Mullady et al., 2011). No studies have been found on this relationship among adult individuals with other kinds of chronic pain. The purpose of the present study was to describe the characteristics of chronic pain, including pattern, severity, location, spread, and duration in a large nationwide population-based sample and to investigate the relationships between the pain pattern and impact on the individual’s daily life and HRQoL.
METHODS Sample and Data Collection Procedures A sample of 4,500 individuals, aged 20-70 years, was randomly drawn from the Icelandic National Registry. The National Registry holds information about names, birth dates, and addresses of all residents of Iceland. To secure a proportional sample of men and women and people from all regions of the country, the sample was stratified in relation to gender and residence. The participants were sent an information letter and a questionnaire in which they were asked to answer questions on HRQoL and whether they had felt pain during the previous week. Participants were given two response options, either filling out the questionnaire and sending by post or logging into a website and answering online. Responders who reported pain during the previous week were asked to answer questions on duration of pain, location, severity, interference with different activities of daily life, and pattern of pain. Questionnaires were marked with an
Chronic Pain Pattern and Health-Related Quality of Life
identifying number on the back side to be able to trace response rate while still ensuring privacy. To improve response rate, individuals who did not respond within two weeks received a reminder postcard, and those who had not responded within four weeks received a new questionnaire along with an information letter. The study was approved by the Icelandic National Bioethics Committee (VSNb2011030002/03.7) and the Icelandic Data Protection Authority (S5197/2011). Completing and returning the questionnaire was considered to imply informed consent for participation in the study. Instruments This study is part of more extensive research on chronic pain and HRQoL, as well as access to and use of health care and patient-provider communication. The instruments consist of questionnaires on pain, HRQoL, access to and use of health care service both generally and in relation to pain, patient-provider communication, and sociodemographic data. Data on sociodemographic characteristics, pain measures, and HRQoL are presented in this paper. Sociodemographic Characteristics. The sociodemographic data collected were age, gender, marital status, and education. Pain Severity and Interference with Life. The Icelandic version of the Brief Pain Inventory (BPI) was used to evaluate pain severity and interference with life (Cleeland & Ryan, 1994; Gunnarsdottir, Ward, & Serlin, 2008). Participants also were asked to answer questions about the duration and location of pain. The BPI contains three questions regarding pain severity during the previous 24 hours, worst pain, least pain, and average pain. The fourth severity item measures pain at present. Participants rate their pain on a scale from 0 to 10, where 0 indicates no pain and 10 is the worst pain imaginable. Interference with life is evaluated by questions on the impact of pain on seven aspects of daily life: mood, walking ability, work, social activity, sleep, and life enjoyment. Participants rate the impact of pain on these seven items on a scale from 0 to 10, anchored with ‘‘does not interfere’’ (0) and ‘‘completely interferes’’ (10) (Cleeland & Ryan, 1994). By taking the mean of the four severity items and the seven interference items separately, two composite scores, the Pain Severity Index and the Pain Interference Index, are calculated (Zelman, Gore, Dukes, Tai, & Brandenburg, 2005). The BPI has been translated into Icelandic and validated in a general population sample of Icelandic adults experiencing pain of various origins and found to be both reliable and valid (Gunnarsdottir et al., 2008). In the present study, the internal consistency was a ¼ 0.89
3
for the severity scale and a ¼ 0.91 for the interference scale. In the Icelandic version, the time reference used is the past week as opposed to the past 24 hours in the English version (Gunnarsdottir et al., 2008). Health-Related Quality of Life. The Short Form 36 Health Survey (SF-36v2) is a 36-item self-rating questionnaire developed to assess some primary aspects of HRQoL, perceived health status in various health conditions, and diseases (Beaton, Hogg-Johnson, & Bombardier, 1997; Vetter, 2007). The instrument comprises 36 multiple choice questions, and responses vary from yes or no answers to a six-point rating scale (ordinal) (Beaton et al., 1997). Questions are designed to assess eight different health domains: (1) physical functioning (PF, 10 questions); (2) role physical (RP, 4 questions); (3) bodily pain (BP, 2 questions); (4) general health (GH, 5 questions); (5) vitality (VT, 4 questions); (6) social functioning (SF, 2 questions); (7) role emotional (RE, 3 questions); and (8) mental health (MH, 5 questions). In addition, there is one single question asking respondents to compare their health now with how it was one year ago on a scale from 1-5 (Wallin & Raak, 2008; Ware, 2000). Each dimension is scored from 0 (worst) to 100 (best possible health status) (Jenkinson, Stewart-Brown, Petersen, & Paice, 1999; Ware, 2000). The eight domains are hypothesized to form two distinct higher-order clusters due to the physical and mental health variance that they have in common (Ware, 2012) The reliability and validity of the instrument in relation to different health conditions has been widely tested and confirmed (Beaton et al., 1997; Ware, 2012). In the present study the internal consistency was acceptable for all scales, with Chronbach’s alpha ranging from 0.78 (GH) to 0.94 (RP). Pattern, Location and Spread of Pain. Respondents were asked to answer a question about the pattern of pain, classified as constant pain (pain all the time), daily intermittent (daily pain with one to a few hours break during the day), frequent intermittent (pain most days but pain-free days in between), and periodic (pain-free periods for days or weeks but pain episodes in between). Location of pain was classified by asking participants to indicate all areas of the body where they sensed pain by marking them on a list of 19 areas of the body (e.g., head, neck, hand/hands, foot/feet etc.). Spread of pain was classified as number of pain locations. Statistical Analyses Data were analyzed using SPSS for Windows (version 20.0). Descriptive statistics were used to present the sample’s demographic characteristics and causes,
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duration, location, spread, pain pattern, pain severity, as well as interference with life and HRQoL in relation to pain. ANOVA and trend analyses were used to check for relationships between pain pattern, interference with life, and HRQoL. Predictors of interference with life and HRQoL (SF-36 scores) were calculated by means of a hierarchical stepwise regression analysis, in which the predictors of interest—pattern, severity, and spread of pain—were entered in steps one to three and controlled for demographic variables (gender, age, education) by entering them in the final fourth step.
RESULTS Response Rate Of the 4,500 questionnaires mailed, a total of 1,629 questionnaires were returned (37.9%). Of the returned questionnaires, 63 were incomplete and 1,586 were completed (36.9%) (Fig. 1). Of 4,500 individuals in the original sample, 564 were considered of non-Icelandic origin. Only 43 (8.6%) of these returned a filled questionnaire. The questionnaires were only in Icelandic, and although only one person reported being unable to participate because of lack of proficiency in Icelandic, it can be assumed that the low response rate in this group was probably due to language difficulties. The calculation of response rate without participants of non-Icelandic origins would have been higher (40.6%). However, in an attempt to preserve a multicultural approach, it was decided to include all in the sample. The inclusion process of participants is outlined in Figure 1. Characteristics of the Sample (n ¼ 1,586) Most respondents who returned a completed questionnaire were women (56.5%). The total sample mean age was 46.2 years (SD ¼ 13.99, range 20-70 years; women: 45.3, men: 47.3). Respondents were significantly older than nonrespondents (mean age of nonparticipants, 38.7; p < .005), and response rate was lower among younger individuals and men. Differences between age distribution of respondents and nonrespondents are listed in Table 1. Most respondents were married or cohabitating, 27.3% had less than 11 years of school education. Sociodemographic characteristics (gender, age groups, marital status, and education) are listed in Table 1. Duration and Causes of Pain From the total sample of respondents (n ¼ 1,586), 873 persons (55.0%) reported that they had felt some kind of pain (other than minor headache, sprain, toothache, or menstrual pain) during the previous week. A similar number (n ¼ 828, 52.2%) reported that they had been
diagnosed with some chronic disease or health problem, with hypertension (n ¼ 374, 23.6%) and rheumatism (n ¼ 200, 12.6%) most frequently reported. Of those who answered the question on duration of pain (n ¼ 816), most 92.4% (n ¼ 754) had pain for three months or longer. Only 62 (7.6%) reported pain for less than three months. The total prevalence of chronic pain ($3 months) was 47.5% (n ¼ 754) with mean duration of 9.3 years (median ¼ 6 years, SD ¼ 10). The prevalence of pain in relation to demographic characteristics is listed in Table 1. The most frequently reported causes of chronic pain were myalgia (n ¼ 289, 41.1%), old trauma (n ¼188, 26.7%), wear and tear (n ¼176, 25.0%), osteoarthritis (n ¼ 168, 23.9%), and fibromyalgia (n ¼ 90, 12.8%). Pain Locations and Spread The most frequently reported location of chronic pain was low back (61.5%). Other frequently reported locations were shoulders (45.6%), neck (35.7%), head (32.4%), and knee (35.7%). Few (12%) reported one location of pain. One third (30.2%) reported pain in 2-3 locations, and another third (32.1%) reported pain in 4-6 locations. Pain Severity, Duration, and Interference with Life and HRQoL The mean value for the pain severity index for participants reporting pain $3 months was 3.4 (SD ¼ 1.83) and 2.6 (SD ¼ 2.20) for the interference index. For those who reported pain <3 months, these numbers for the pain severity index were 2.4 (SD ¼1.70) and the interference index 1.6 (SD ¼ 1,69). Both indices increased with longer duration of pain, and the differences were significant between groups reporting pain for shorter or longer than three months (p < .01). There was a significant difference in all SF-36 subscales between those reporting pain during the previous week and those with no pain during the previous week (p < .01), with the former group reported higher interference with life and lower HRQoL than the latter. There was also a significant difference in the interference with life scale and in all SF-36 subscales (p < .01) between groups reporting pain for <3 months or $3 months, except for Role Emotional subscale (p ¼ .07). Table 2 shows an overview of HRQoL and interference with life in relation to pain duration. Pain Pattern, Interference with Life, and HRQoL Of those who reported pain during the previous week, almost one third (29.8%) reported the pain to be
Chronic Pain Pattern and Health-Related Quality of Life
FIGURE 1.
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5
Flow chart of study participants.
constant and one fifth (22.5%) reported periodic pain with pain-free days or weeks in between. One third (31.9%) of those reporting pain for $3 months reported constant pain and only 18.9% reported pain to be periodic. Among those reporting pain for less than 3 months, periodic (52.5%) and frequent intermittent (22%) were the most common pain patterns. Patterns of chronic pain in relation to demographic information (gender and education) are listed in Table 3. The relationships between different patterns and interference with life as well as HRQoL subdomains are shown in Table 4. As shown in Table 4, participants reporting constant pain had the highest values in
interference with life and lowest values in all HRQoL subdomains. Prediction of Interference with Life and Domains of HRQoL Tables 5 and 6 summarize hierarchical regression models showing the predictors that were included in the stepwise regression analyses. In the first step, pattern variables (constant, daily intermittent, and frequent intermittent versus periodical pain) were entered. All patterns were significantly related to interference with life and all domains of HRQoL. However, the strength of this relationship was different in different domains, being higher in the physical domains
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TABLE 1. Demographic Information for Respondents and Nonrespondents
Gender Female Male Age groups 20-30 31-40 41-50 51-60 61-70 Marrital status Married/cohabit Single Divorced Widowed Education Lower secondary school (#10 years) Upper secondary school general (>10 years) Upper secondary school occupational (>10 years) University #4 years University >4 years
Respondents Completed Lists (%)
Non respondents (%)
Total in Sample
Pain Last Week (%)
Pain $3 Months (%)
875 (40.7) 673 (30.0)
1273 (59.3) 1569 (70.0)
2148 2242
501 (57.3) 358 (53.2)
435 (49.7) 307 (45.6)
274 (21.8) 270 (26.3) 355 (40.7) 345 (44.1) 303 (54.1)
984 (78.2) 757 (73.7) 518 (59.3) 437 (55.9) 257 (45.9)
1258 1027 873 782 560
138 (50.4) 140(51.9) 204 (57.5) 198 (57.4) 179 (59.1)
114 (41.6) 123 (45.6) 169 (47.6) 179 (51.9) 157 (51.8)
1139 (73.7) 281 (18.2) 98 (6.3) 28 (1.8)
647 (56.8) 142 (50.5) 53 (54.1) 16 (57.1)
556 (48.8) 128 (45.6) 43 (43.9) 15 (53.6)
417 (27.3)
254 (60.9)
222 (53.2)
191 (12.5)
100 (52.4)
83 (43.5)
432 (28.3)
258 (59.7)
219 (50.7)
298 (19.5) 191 (12.5)
159 (53.4) 80 (41.9)
147 (49.3) 63 (33.0)
(PF, RP, BP, and GH) compared with the mental domains (VT, SF,RE, and MH). The coefficient for variance of pain pattern alone, in relation to interference with life and different HRQoL domains was lowest in MH (R2 ¼ .035) and RE (R2 ¼ .054) and highest in BP (R2 ¼ .296) and RP (R2 ¼ .147) (Table 6). Steps 2 and 3 show the additional variance explained by pain severity and spread. As shown in
Table 5, severity turned out to be the most important factor for interference with life. Pattern alone explained 18.3% of variance; pain pattern and pain severity explained 44.4%, and after adding spread of pain, the variance explained was 45.2%. Severity was also the strongest predictor in most HRQoL domains, which can be seen in the change in R2 between step 2 and 3 in Table 6. Spread of pain did not add much
TABLE 2. Pain Duration Versus Interference with Life and HRQoL (SF-36 Scores) Duration of pain Variable
Total Score Mean (SD)
No Pain Previous Week
Pain Previous Week
Pain <3 Months
Pain $3 Months
Interference with life Physical functioning Role physical Bodily pain General health Vitality Social functioning Role emotional Mental health
2.46 (2.17) 84.65 (22.29) 78.87 (26.36) 68.84 (25.63) 69.39 (21.45) 57.67 (20.72) 81.62 (22.69) 84.03 (23.09) 75.53 (17.85)
— 92.81 (16.32) 89.53 (17.47) 85.53 (17.47) 77.45 (17.37) 64.78 (18.25) 87.61 (18.46) 8854 (19.78) 78.68 (15.88)
2.54 (2.18) 79.54 (23.57) 71.19 (28.93) 56.87 (24.14) 64.34 (22.33) 52.90 (20.81) 77.40 (24.37) 81.34 (24.19) 73.29 (18.97)
1.62 (1.70) 89.30 (17.5) 84.02 (20.74) 69.72 (20.88) 73.91 (19.45) 61.67 (18.81) 86.42 (18.77) 87.89 (20.31) 77.93 (13.44)
2.63 (2.20) 78.37 (24.00) 69.75 (29.51) 55.41 (24.29) 63.21 (22.50) 51.79 (2098) 76.53 (24.77) 80.62 (2435) 72.88 (13.44)
Note. Interference with life is measured on a 0-10 scale. HRQoL (SF-36 scales) is measured on a 0-100 scale.
7
Chronic Pain Pattern and Health-Related Quality of Life
TABLE 3. Pattern of Chronic Pain Pain Pattern ($3months) Variable
Constant Pain (%)
Daily Intermittent (%)
Frequent Intermittent (%)
Periodal (%)
Pain $3 months (n ¼ 705) Gender (n ¼ 753) Men (n ¼ 311) Women (n ¼ 442) Education (n ¼ 745) Lower secondary school (#10 years) Upper secondary school general (>10 years) Upper secondary school occupational (>10 years) University #4 years University >4 years
225 (31.9)
151 (21.4)
196 (27.8)
133 (18.9)
83 (29.3) 140 (34.0)
55 (19.4) 93 (22.6)
82 (29.0) 110 (26.7)
63 (22.3) 69 (16.7)
83 (40.9)
46 (22.7)
47 (23.2)
27 (13.3)
25 (32.9)
15 (19.7)
18 (23.7)
18 (23.7)
60 (29.3)
44 (21.5)
59 (28.8)
42 (20.5)
37 (25.5) 16 (27.6)
31 (21.4) 10 (17.2)
53 (36.6) 15 (25.9)
24 (16.6) 17 (29.3)
to the variance explained, except for the VT and RE domains, in which spread was a stronger predictor than severity. In step 4, demographic variables (gender, age, education) were entered. None of these variables had a significant influence on the relationship between interference with life and any of the research variables (pattern, severity, spread). Gender was not significantly related to any of the HRQoL domains. Age was significantly related to PF, VT, and MH, although the relationship was weak. Education was not significantly related to any domains except PF and RE. Although the pain pattern was a significant predictor for the relationship between chronic pain and interference with life as well as in all HRQoL domains, this became mostly nonsignificant when pain severity was added to the regression model in step 2. Severity was significantly related to both interference with life score and all HRQoL domains. Spread of pain added little to the variance of research variables, except for the VT and RE domains. Severity was the strongest predictor in most domains, as seen in the change in R2 between steps 1 and 2.
DISCUSSION The aim of the present study was to describe the characteristics of chronic pain, including pattern, severity, location, spread, and duration in a nationwide population-based sample and to investigate the relationships between pain pattern and impact on the individual’s life as measured by interference with life and HRQoL. This study is the first to measure the
characteristics of chronic pain in a large sample of the Icelandic general population. This is also the first population-based study investigating the impact of pain pattern on the relationship between chronic pain and interference with life and HRQoL. Prior work on the relationship between chronic pain and HRQoL has documented the importance of pain severity and spread in the relationship between chronic pain and HRQoL (Bergman et al., 2004; Jamison et al., 2007; Lame et al., 2005; Laursen et al., 2005). In some studies, however, pain severity alone has, been shown to be a weak predictor in the relationship between pain and HRQoL (Lame et al., 2005) and significant only if in relation to spread (Bergman et al., 2004). In the present study, the interplay between pain severity and number of pain locations as predictors for the relationship between chronic pain and HRQoL was different from what has been reported in earlier studies. The fact that earlier studies have not considered the influence of pain pattern in this relationship might be the explanation for this difference. When pain severity was added to the regression model, there was a significant increase in variance both in the interference scale as well as in all domains of HRQoL, indicating that pain severity in relation to pain pattern significantly predicts the relationship between chronic pain and its influence on the individual’s life. Finally, when the number of pain locations was added to the regression model, the difference in variance was much less than for pain severity, although significant. In the present study, more than half of respondents reporting chronic pain ($3 months) had constant or
8
Jonsdottir et al.
TABLE 4. Scores of Interference and SF-36 Scales in Relation to Pain Pattern. ANOVA and Linear Trend Analyses Variable Interference with life Constant pain (n ¼ 187) Daily intermittent (n ¼ 138) Frequent intermittent (n ¼ 179) Periodal (n ¼ 117) Physical Functioning Constant pain (n ¼ 223) Daily intermittent (n ¼ 148) Frequent intermittent (n ¼ 194) Periodal (n ¼ 133) Role Physical Constant pain (n ¼ 221) Daily intermittent (n ¼ 149) Frequent intermittent (n ¼ 192) Periodal (n ¼ 132) Bodily Pain Constant pain (n ¼ 225) Daily intermittent (n ¼ 148) Frequent intermittent (n ¼ 194) Periodal (n ¼ 132) General Health Constant pain (n ¼ 225) Daily intermittent (n ¼ 151) Frequent intermittent (n ¼ 196) Periodal (n ¼ 133) Vitality Constant pain (n ¼ 224) Daily intermittent (n ¼ 149) Frequent intermittent (n ¼ 194) Periodal (n ¼ 132) Social Functioning Constant pain (n ¼ 225) Daily intermittent (n ¼ 149) Frequent intermittent (n ¼ 194) Periodal (n ¼ 132) Role Emotional Constant pain (n ¼ 220) Daily intermittent (n ¼ 147) Frequent intermittent (n ¼ 191) Periodal (n ¼ 131) Mental Health Constant pain (n ¼ 224) Daily intermittent (n ¼ 148) Frequent intermittent (n ¼ 194) Periodal (n ¼ 132)
Mean Score
SD
3.75 3.05 1.99 1.23
2.46 2.00 1.78 1.30
67.56 74.83 86.34 87.44
26.98 22.65 15.99 19.83
57.28 61.65 78.45 84.67
30.55 30.65 24.36 20.50
40.57 46.34 64.16 72.79
23.19 20.33 15.96 18.47
55.88 58.63 67.83 72.03
24.20 21.14 20.14 17.92
43.47 49.45 55.28 61.04
21.21 20.12 19.67 17.04
68.28 76.26 79.45 84.75
27.92 23.95 21.64 18.49
72.58 80.41 83.27 88.00
29.49 24.42 20.49 17.02
68.12 74.49 73.06 77.96
21.21 18.55 18.08 15.65
Linear Trend p Value <.001
<.001
<.001
<.001
<.001
<.001
<.001
<.001
<.001
Note: Interference with life is measured on a 0-10 scale. HRQoL (SF-36 scales) is measured on a 0-100 scale.
daily pain. This is similar to results from a large population-based study on the prevalence and characteristics of chronic pain in 15 European countries and Israel, in which approximately half of the participants reporting chronic pain ($6 months) had constant pain (Breivik et al., 2006). The results show that pain pattern is an important factor in the relationship between chronic pain and interference with life as well as all domains of HRQoL. This accounts for both
physical and psychosocial domains, even when controlled for gender, age, and education, and these influences are stronger the more constant the pain is. Constant and daily pain significantly influences the relationship in interference with life as well as in all HRQoL domains. Frequent intermittent or periodic pain has less influence, but also significant, in the interference with life scale as well as the bodily pain, vitality, and mental health HRQoL scales.
9
Chronic Pain Pattern and Health-Related Quality of Life
TABLE 5. Summary of the Hierarchical Regression Analyses for Interference with Life Model 1 Variable
p
B
Interference with life, N ¼ 620 Constant Pain pattern Constant pain vs. Periodical Daily intermittent vs. Periodical Frequent intermittent vs. Periodical Severity Spread Gender Age Education U secondary vs. L secondary U occupational vs. L secondary University <4 vs. L secondary University >4 vs. L Secondary R2 p value for change in R2
Model 2 p
B .271
1.267 2.447 1.806 .711
Model 3
<.001 <.001 .003
.183 <.001
Model 4 p
B .391
p
B .221
.550 .550 .291
.013 .013 .144
.470 .497 .296
.035 .025 .134
.448 .510 .303
.044 .022 .126
.733
<.001
.689 .062
<.001 .003
.698 .064 .178 .005
<.001 .003 .199 .379
.250 .362 .102 .120
.317 .037 .603 .649
.444 <.001
.452 .003
.459 .240
Note: Interference with life is measured on a 0-10 scale.
This study shows that pain pattern and pain severity are significant predictors for the impact of chronic pain on an individual’s daily life. As pain becomes more constant and pain severity increases, there are more detrimental influences. Pain pattern in relation to pain severity accounts for as great as a 44.4% variance for interference with life, and the number of pain locations adds very little to this relationship. Pain pattern and pain severity account for 20.4%-53.3% of variance in physical domains of HRQoL (PF, RP, BP, and GH). In the four psychosocial domains (VT, SF, RE, and MH), pattern, severity and spread account for less variance in the relationship between pain and HRQoL than in the physical domains. In the SF and MH domains,
pattern and severity account for 16.5% and 7.3% of variance, respectively. The two other psychosocial domains, VT and RE, are the only domains of HRQoL in which spread of pain is a more important indicator than severity. In these two domains, pattern and spread account for 17.6% and 10.6% of variance, respectively. In the present study, pain pattern and severity had a stronger relationship with the physical domains of HRQoL than the mental domains. On the other hand, pain spread is a more important factor than severity in the relationship between chronic pain and at least some of the mental domains. Similar results regarding the importance of pain spread in the relationship
TABLE 6. Summary of the Hierarchical Regression Analyses for SF-36 Scales R2/p Value for Change in R2 (N ¼ 674) Evaluation Criteria
Model 1
Model 2
Model 3
Model 4
Physical Functioning Role Physical Bodily Pain General Health Vitality Social Functioning Role Emotional Mental Health
.132/<.001 .147/<.001 .296/<.001 .085/<.001 .099/<.001 .061/<.001 .054/<.001 .035/<.001
.279/<.001 .323/<.001 .533/<.001 .204/<.001 .176/<.001 .165/<.001 .106/<.001 .073/<.001
.301/<.001 .351/<.001 .543/<.001 .243/<.001 .214/<.001 .185/<.001 .127/<.001 .090/.001
.328/<.001 .354/.756 .545/.791 .259/.028 .257/<.001 .201/.047 .159/<.001 .150/<.001
10
Jonsdottir et al.
between chronic pain and the mental components of HRQoL, especially, were reported by Bergman et al., 2004. This might indicate that pain characteristics (e.g., severity and spread) influence physical and mental components of each individual’s life differently. The results of the present study indicate that pain pattern is an important factor in how chronic pain influences the individual’s daily life—the more constant the pain, the more detrimental the effects. It also is important to notice that more than half (53.3%) of participants experiencing chronic pain had constant or at least daily pain and that most individuals with pain duration less than 3 months reported periodic pain. This indicates that as pain is prolonged, the risk for constant or daily pain increases. This is important to notice in the clinical practice. When the patient seeks care for pain, it is necessary to approach pain in a broad spectrum and consider different characteristics and its effects on daily life. This is important to prevent pain from becoming chronic, constant, or daily in pattern. Earlier studies also have suggested the urgency of a preventive perspective in the clinical assessment of prolonged pain (Bergman et al., 2004; Peolsson et al., 2007). There are a number of limitations to the present study that should be taken into account. The crosssectional design of this study makes causal inferences impossible. The major limitation is the relatively low response rate despite careful attention given in the study design to maximizing the number of responses. It was possible to compare responders and nonresponders in terms of age and gender, and a significant difference between those who responded and those who did not was found. The response rate was 40.7% among women and 30.0% among men, and the responders were significantly older than nonresponders, with a 21.8% response rate in the youngest age group (20-30 years) and 54.1% in the oldest group (61-70 years). Prior studies on the prevalence of pain have shown a similar pattern (Rustoen et al., 2004). It is also worth noting that most respondents reporting pain had felt pain for three months or longer, making the prevalence of chronic pain relatively high compared with the occurrence of pain of shorter duration. Based on this, it can be speculated whether those who
were invited to participate were more likely to do so if they felt pain and had done so for a long time and, therefore, felt that they had some investment in the topic. Another important issue in relation to the low response rate is that, among the total of 4,500 individuals, 564 were considered to be of non-Icelandic origin. Among these individuals, the response rate was much lower than in the total sample, indicating that the reason for the relatively low total response rate might in part be language difficulties. This study is the first general population-based study investigating the impact of pain pattern on the relationship between chronic pain and interference with life and HRQoL. It is also the first to evaluate the characteristics of chronic pain in a large sample in the Icelandic general population. It thereby contributes valuable knowledge on the impact of pattern of chronic pain on individuals’ daily lives and HRQoL in a large population-based sample.
CONCLUSIONS This study found a significant impact of pain pattern on the relationship between chronic pain and interference with life and different domains of HRQoL and how pain severity adds to this relationship. This is important to notice in the clinical practice related to individuals with chronic pain and to approach pain in a broad spectrum and consider different characteristics of pain and its effect on the individual’s different aspects of life. Further studies should be carried out investigating the relationship between pain and interference with life and HRQoL among individuals experiencing chronic pain. For example, a longitudinal study might be conducted on changes in pain pattern over time and how these changes influence the impact of pain on an individual’s life over time. A qualitative approach in which individuals experiencing chronic pain were asked to describe the pattern of their pain and how it influences their daily life activities in their own words would deepen the knowledge in this area. Acknowledgments We are grateful to all those who participated in this study.
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