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Association between daily pain and physical function among old–old adults living in the community: Results from the ilSIRENTE study
Pain 121 (2006) 53–59 www.elsevier.com/locate/pain
Association between daily pain and physical function among old–old adults living in the community: Results from the ilSIRENTE study Graziano Onder
b
a,*
, Matteo Cesari a,b, Andrea Russo a, Valentina Zamboni a, Roberto Bernabei a, Francesco Landi a
a Department of Gerontology, Catholic University of Sacred Heart, Rome, Italy Department of Aging and Geriatric Research, University of Florida, College of Medicine, Gainesville, FL, USA
Received 12 April 2005; received in revised form 18 November 2005; accepted 5 December 2005
Abstract Little is known about the impact of pain on physical function among old–old subjects. The aim of the present cross-sectional study was to assess the association of daily pain with muscle strength and physical performance in a population of subjects aged 80 or older living in the community. We used data from baseline evaluation of the ilSIRENTE Study. Muscle strength was measured by hand grip strength. Physical performance was assessed using the physical performance battery score, which is based on three timed tests: 4-m walking speed, balance, and chair stand tests. Daily pain was defined as any type of pain or discomfort in any part of the body manifested every day over the 7 days preceding the assessment. Mean age of 273 participants was 85.1 (SD 4.6) years, 181 (66.3%) were women and 150 (54.9%) reported daily pain. After adjustment for potential confounders, participants with daily pain had lower grip strength and physical performance battery score (indicating worse performance) than other participants (hand grip strength: daily pain 31.5 kg, SE 1.4, no daily pain 35.0, SE 1.1, p = 0.02; physical performance battery score: daily pain 6.5, SE 0.3, no daily pain 7.2, SE 0.3, p = 0.05). Both hand grip strength and physical performance battery score progressively declined as pain severity increased. In conclusion, the present study shows that among old–old subjects living in the community, daily pain is highly prevalent and that this condition is associated with impaired muscle strength and physical performance. Ó 2005 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. Keywords: Elderly; Physical performance; Muscle strength
1. Introduction Pain in the older population is a major health issue, both because of its high prevalence and impact on physical and psychological well being (Gureje et al., 1998). It has been estimated that in older populations, the prevalence of pain ranges from 45% to 80%, depending on age, setting, and country of residence (Bernabei et al., 1998; Landi et al., 2001; Thomas et al., 2004). In addi*
Corresponding author. Tel.: +39 06 30154341; fax: +39 06 3051911. E-mail address: [email protected] (G. Onder).
tion, this condition has been proved to interfere with daily activities, cause depression and emotional distress, leading to increased costs related to caregiver burden, long-term institutionalization, and physicians referral (Won et al., 1999; Lamb et al., 2000; Al Snih et al., 2001; Leveille et al., 2001; Reyes-Gibby et al., 2002; Weiner et al., 2004; Onder et al., 2005a). Despite these considerations, physicians frequently fail to accurately diagnose and treat pain, particularly among older adults: it has been shown that independently of clinical setting and clinical diagnoses, one-quarter of older adults with pain does not receive any analgesic drugs and those older than 85 years are even less likely
0304-3959/$20.00 Ó 2005 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.pain.2005.12.003
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to receive any treatment (Bernabei et al., 1998; Landi et al., 2001). These data, along with the emphasis on pain as the fifth vital sign by the Veteran’s Administration and the attention on pain assessment by Joint Commission on Accreditation of Healthcare Organization, highlight the importance of a better assessment of pain and its correlates, particularly among old–old subjects, that represent a progressively growing population often not adequately represented in epidemiological studies (Health agencies update, 1999; Joint Commission on Accreditation of Health Care Organizations, 2000). In this context, little is known about the impact of pain on physical function among old–old subjects. Therefore, the aim of the present cross-sectional study was to assess the association of pain with muscle strength and physical performance in a population of subjects aged 80 or older living in the community. 2. Methods The ilSIRENTE study is a prospective cohort study performed in the mountain community living in the Sirente geographic area (L’Aquila, Abruzzo) in Central Italy. This study was designed by the Department of Gerontology of the Catholic University of Sacred Heart (Rome, Italy) and developed by the teaching nursing home Opera Santa Maria della Pace (Fontecchio, L’Aquila, Italy) in a partnership with local administrators and primary care physicians of Sirente Mountain Community Municipalities. All the participants signed an informed consent at the baseline visit. Details of the ilSIRENTE study protocol are described elsewhere (Landi et al., 2005). 2.1. Study population A preliminary list of all community dwelling older adults living in the Sirente area was obtained at the end of October 2003 from the Registry Offices of the 13 municipalities involved in the study. From this preliminary list, potential study participants were identified by selecting all persons born before January 1st, 1924 living in the Sirente area. Of the initial 514 subjects screened, 32 men and 53 women died or moved away from the area before the baseline assessment. Among those eligible (n = 429), prevalence of refusals was very low (16%). Subjects participating in the study did not differ significantly from those who refused to participate by age and gender. As a result, the overall sample population enrolled in the ilSIRENTE study consisted of 364 subjects. 2.2. Data collection Baseline participants’ assessments began in December 2003 and were completed in September 2004. Assessors were trained on how to perform each component of the ilSIRENTE study protocol. The Minimum Data Set for Home Care (MDSHC) form was administered to all study participants, following the guidelines published in the MDS-HC manual (Morris et al., 1996, 1997). The MDS-HC contains over 350 data elements including socio-demographics, physical and cognitive
status variables, as well as major clinical diagnoses (Morris et al., 1996). Moreover, the MDS-HC also includes information about an extensive array of signs, symptoms, syndromes, and treatments (Morris et al., 1996). Clinical diagnoses were recorded by a study physician gathering information from the patient, the general practitioner and after physical examination, careful review of patient clinical documentation (including laboratory tests and X-rays) and based on previous medical history. The cognitive performance scale (CPS) was used to assess cognitive status (Hawes et al., 1995). The CPS has shown an excellent inter-rater and test–retest reliability when completed by nurses performing usual assessment duties (Hawes et al., 1995; Landi et al., 2000). The CPS score ranges from 0 (intact cognition) to 6 (severe dementia). We categorized cognitive status as follows: normal (CPS score of 0–1), moderately impaired (CPS score of 2–4), and severely impaired (CPS score of 5–6). The depression rating scale was used to assess the presence of depressive symptoms (Burrows et al., 2000). Based on a previous observation, participants with a score P3 were diagnosed as depressed. The depression rating scale has proven reliable for detecting depression among older adults (Burrows et al., 2000). Participants reporting light intensity (aerobic) exercise performed for at least 2–4 h per week during the last year were defined physically active. Activities of daily living (ADL) considered for this study were dressing, eating, toilet use, bathing, mobility in bed, locomotion, and transfer. Impairment in each ADL was defined as the need of assistance to complete the task. Data on medications taken in 7 days prior to the assessment were also collected and coded according to the Anatomical Therapeutic and Chemical codes (Pahor et al., 1994). Analgesics were classified into three different groups according to the WHO 3-step ladder, including nonopioids (level 1; e.g., salicylates and nonsteroidal anti-inflammatory drugs), weak opioids (level 2; e.g., codeine phosphate, pentazocine hydrochloride, and buprenorphine hydrochloride), and strong opioids (level 3; e.g., morphine sulfate, hydromorphone hydrochloride, fentanyl citrate, and methadone hydrochloride). 2.3. Assessment of pain Pain was defined as any type of pain or discomfort in any part of the body that was manifested over the 7 days preceding the assessment (Morris et al., 1996). As part of the standard MDS assessment, the study physician was instructed to ask simple and direct questions about whether the participant experienced pain. Among participants unable to talk or lacking the ability to adequately describe symptoms, the assessors were also instructed to observe for indicators of pain, including moaning, crying, wincing, frowning, other facial expressions or posturing such as guarding or protecting an area of the body. Pain frequency was coded as less than daily, daily with a single episode or daily with multiple episodes. To avoid misclassification of pain, subjects with cognitive impairment, defined as CPS score P2, were excluded from the study (n = 91). For the purpose of this study we compared subjects experiencing ‘daily pain’ (n = 150) with those experiencing pain less than daily or without pain (‘no daily pain’ n = 123). Pain severity was coded as mild, moderate, severe or excruciating; number of painful sites was coded as single or multiple. Datum on sites
G. Onder et al. / Pain 121 (2006) 53–59
with pain was missing for one participant. Independent, dual assessment of pain items (including presence of pain, pain frequency, severity, and number of sites with pain) in a diverse sample of patients during testing and revision of the MDS showed an average weighted Kappa exceeding 0.7 (Morris et al., 1997). 2.4. Outcome measures Physical performance battery – Physical performance was assessed by the physical performance battery score. This latter is composed by three timed tests: 4-m walking speed, balance, and chair stand tests. Timed results from each test were rescored from 0 (worst performers) to 4 (best performers). The sum of the results from the three categorized tests (ranging from 0 to 12) was used for the present analyses (Guralnik et al., 1995; Onder et al., 2002). Categorization of results from 4-m walking speed and chair stand tests was obtained on the basis of the ilSIRENTE population-specific quartiles. The balance test was categorized according to previously established cut-points provided by Guralnik et al. (1995). Muscle strength measure – Grip strength was used as an indicator of muscle strength. Grip strength was known to be positively correlated with lower extremity strength and performance in older persons (Era et al., 1992; Rantanen et al., 1994; Visser et al., 2000) and this measure has shown to be predictive of major health-related events in older persons; (Rantanen et al., 1999; Al Snih et al., 2004). Moreover, grip strength is a reliable and portable muscle strength test that can be administered in a home setting (Al Snih et al., 2004). Grip strength was assessed by hand grip strength measured by a dynamometer. 2.5. Statistical analysis To avoid misclassification of pain, from the initial sample of 364 participants, we excluded 91 subjects with cognitive impairment, defined as CPS score P2. In the remaining sample, differences in proportions and means of covariates between participants with (n = 150) and without daily pain (n = 123) were assessed using Fisher’s Exact Test and t test statistics, respectively. Analysis of covariance (ANCOVA) was used to calculate adjusted means of hand grip strength and physical performance battery score according to presence of daily pain, pain severity, and number of sites with pain. Variables considered for adjustment were those associated with daily pain at p 6 0.10 at the univariate analysis and those thought to be clinically significant. Final analyses were adjusted for age, gender, cognitive performance scale score, osteoarthritis, depression, physical activity, and body mass index. All analyses were performed using SPSS software (version 9.0, SPSS Inc., Chicago, IL).
3. Results Mean age of 273 subjects participating the study was 85.1 (SD 4.6) years, and 181 (66.3%) were women. Of the total sample, 150 subjects (54.9%) presented with daily pain; 110 subjects (40.3%) defined daily pain as mild or moderate and 40 (14.7%) severe or excruciating.
55
Daily pain was limited to a single site in 24 cases (8.8%) and involved multiple sites in 125 cases (45.8%). Characteristics of the study population according to the presence of daily pain are summarized in Table 1. Compared with participants without daily pain, those with daily pain were younger, more likely to be women, and had higher prevalence of osteoarthritis and depression. No significant difference between the two study groups was observed for other medical conditions. In addition, subjects with daily pain tended to be less physically active and to have a higher body mass index, compared with other participants. Only 39 participants (26%) reporting daily pain and 9 (7.3%) not reporting daily pain were using pain medications; overall 44 were receiving NSAIDs or acetaminophen (WHO level 1) and 5 weak or strong opiates (WHO levels 2 and 3). In the daily pain group, use of pain medications increased as severity and number of sites with pain increased. Participants with daily pain had significant lower grip strength and physical performance battery score (indicating worse performance) than other participants (hand grip strength: daily pain 29.8 kg, SE 1.0, no daily pain 37.3, SE 1.3, p < 0.001; physical performance battery score: daily pain 6.9, SE 0.3, no daily pain 8.4, SE 0.3, p < 0.001). After adjustment for potential confounders, which included age, gender, cognitive performance scale score, osteoarthritis, depression, physical activity, and body mass index, these associations were still consistent (hand grip strength: daily pain 31.5 kg, SE 1.4, no daily pain 35.0, SE 1.1, p = 0.02; physical performance battery score: daily pain 6.5, SE 0.3, no daily pain 7.2, SE 0.3, p = 0.05). Figs. 1 and 2 report the associations of the outcome measures with pain severity and number of painful sites. As pain severity increased both hand grip strength and physical performance battery score progressively declined (p for trend 0.06 and 0.07, respectively, Fig. 1). Examining the association between these measures and number of sites with pain, we observed a borderline significant trend for hand grip strength (p for trend 0.05) but not for physical performance battery score (p for trend 0.15, Fig. 2). In the fully adjusted models, no significant interaction between gender and pain severity or number of sites with pain was observed. 4. Discussion This is one of the first studies to assess the association of daily pain with physical function among old–old subjects living in the community. We show that daily pain is associated with impaired physical performance and muscle strength, irrespective of potential confounders and that this association gets stronger as pain severity increases. In addition, the association of pain and
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Table 1 Characteristics of study population according to presence of daily pain Characteristics
No daily pain n = 123 (%)
Daily pain n = 150 (%)
P
Age, years (mean ± SD)
85.4 ± 4.9
84.9 ± 4.3
0.37
Female gender
64 (52.0)
117 (78)
<.001
Living alone
48 (39.3)
57 (38.0)
0.82
Cognitive Performance Scale score 0 1
104 (84.6) 19 (15.4)
127 (84.7) 23 (15.3)
Number of impaired ADL (mean ± SD)
0.48 ± 1.55
0.78 ± 1.71
0.13
Diseases Ischemic heart disease Congestive heart failure Hypertension Peripheral vascular disease Stroke Diabetes Chronic obstructive pulmonary disease Parkinson’s disease Cancer Osteoarthritis Depressiona
15 (12.2) 6 (4.9) 94 (76.4) 5 (4.1) 2 (1.6) 29 (23.6) 14 (11.4) 0 (0) 6 (4.9) 10 (8.1) 18 (14.6)
19 (12.7) 7 (4.7) 114 (76.0) 4 (2.7) 4 (2.7) 38 (25.3) 25 (16.7) 4 (2.7) 8 (5.3) 41 (27.3) 49 (32.7)
0.91 0.94 0.94 0.52 0.69 0.74 0.21 0.13 0.87 <.001 0.001
Physical activityb
98 (79.7)
93 (62.8)
0.002
Body mass index, kg/m (mean ± SD)
25.6 ± 3.5
26.2 ± 4.7
0.21
Use of Benzodiazepines Statins Ace inhibitors
9 (7.3) 7 (5.7) 52 (42.3)
17 (11.3) 12 (8.0) 55 (36.7)
0.26 0.46 0.35
2
a b
0.98
Defined as MDS Depression Rating Scale P3. Participants reporting light intensity (aerobic) exercise performed for at least 2–4 h per week during the last year.
muscle strength becomes progressively more pronounced as number of sites with pain increases. Pain may impact on physical function as a consequence of a reduced range of joint movement or reflex inhibition of skeletal muscles, resulting in muscle weakness and impaired strength and physical performance (Young, 1993). Alternatively, pain may limit physical activity and consequently determine a gradual reduction in physical function. Finally, it cannot be excluded that muscle weakness and impaired physical function are directly consequence of medical conditions of late life which are also associated with pain. However, these latter hypotheses are made unlikely by the fact that we adjusted the analyses for indicators of physical activity and comorbid conditions. Results of this study underline the importance of careful assessment of pain when examination of physical function and disability is performed (Flaherty, 2001). Evaluation of pain is easy to perform, relatively cost free, and it can provide precious information: Engle and colleagues have shown that assessment of pain by nursing assistants is unbiased and as accurate as higher-trained medical personnel (Engle et al., 2001). Al Snih and colleagues have proved that asking one simple ques-
tion about presence of pain and discomfort by research assistants who may not have had a medical background may help to predict future disability (Al Snih et al., 2001). These data, along with the observation that pain may impact on physical function and that appropriate pain management results in quicker clinical recovery, shorter hospital stays, fewer readmissions, and improved quality of life (Phillips, 2000), suggest that the assessment and treatment of this condition is extremely rewarding not only for the patients, but also from a health care system prospective. Unfortunately, despite the World Health Organization indicating that almost all patients with malignant pain can be adequately treated by means of simple oral regimens that usually do not produce adverse effects (Stjernsward, 1988), and that non-malignant pain can be effectively managed with both nonpharmacologic and pharmacologic approaches (Blumstein and Gorevic, 2005), these conditions are largely undertreated, particularly in the old–old subjects. In particular, in our study only one-fourth of participants reporting daily pain received pain medications. This result is in line with a previous observation conducted among older adults living in the community in Italy (Landi et al., 2001). However, independently of
G. Onder et al. / Pain 121 (2006) 53–59
30
20
10
30
20
10
0
0 No daily pain (n=123)
p for trend = 0.06
Mild-Moderate (n=110)
6
4
2
0 No daily pain (n=123)
p for trend = 0.07
p for trend = 0.05
Severity of daily pain
p=0.03
8
No daily pain (n=123)
SevereExcruciating (n=40)
Physical Performance Battery score
Physical Performance Battery score
p=0.02
p=0.02
Hand Grip Strength (kg)
Hand Grip Strength (kg)
40
p=0.11
40
57
Mild-Moderate (n=110)
SevereExcruciating (n=40)
Severity of daily pain
Fig. 1. Adjusted means (standard errors) of hand grip strength and physical performance battery score according to severity of daily pain. Analyses are adjusted for age, gender, cognitive performance scale score, osteoarthritis, depression, physical activity, and body mass index.
setting, country, and patients’ characteristics pain is widely undertreated in old populations, and advanced aged seems to reduce the probability to receive adequate analgesic treatment (Bernabei et al., 1998; Won et al., 2004). To assess the effect of pain on physical function, we used the hand grip strength and the physical performance battery score. These two measures of physical function provide a ‘‘multidimensional’’, objective and standardized assessment of older persons, they are able to characterize community dwelling older people across a broad spectrum of functional status and they are sensitive to changes over time (Guralnik et al., 1989, 1994; Onder et al., 2002). In addition, several studies indicated that physical performance measures can complement self-reported measures in the assessment of older persons’ functional status, as suggested by the fact that they tap different, but important, dimensions of physical function (Reuben et al., 1995; Simonsick et al., 2001).
8
Single site (n=24)
Multiple sites (n=125)
Sites with daily pain
p=0.08
6
4
2
0 No daily pain (n=123)
p for trend = 0.15
Single site (n=24)
Multiple sites (n=125)
Sites with daily pain
Fig. 2. Adjusted means (standard errors) of hand grip strength and physical performance battery score according to sites with daily pain. Datum on sites with pain was missing for one participant. Analyses are adjusted for age, gender, cognitive performance scale score, osteoarthritis, depression, physical activity, and body mass index.
In this study, we used grip strength as an indicator of general strength. Although being a direct measure of hand strength, grip strength has frequently been used as an overall measure of body strength, because it is a reliable and portable strength test that can be administered in a home setting (Al Snih et al., 2004). Grip strength in older persons was related to arm flexion (reported correlation coefficients between 0.57 and 0.65), knee extension (0.47–0.51), trunk extension (0.33–0.56), and trunk flexion strength (Era et al., 1992; Rantanen et al., 1994). Physical function measures have gained increased acceptance and use for the clinical evaluation of older persons. In addition, it has been consistently demonstrated that measures of physical function can predict major health-related outcomes in the elderly, such as disability, death, and institutionalization (Guralnik
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et al., 1989, 1995; Rantanen et al., 1999; Al Snih et al., 2004; Onder et al., 2005b). For these reasons, adding an evaluation of physical function to the traditional clinical examination is particularly important in the assessment of older persons. However, the use of such tests in the clinical setting has not been widely adopted possibly owing to the misperception that they often require substantial space, special equipment, or are unduly time consuming. The ilSIRENTE study offers a unique opportunity to investigate factors associated with impaired physical function among old–old and frail subjects, which frequently are excluded from epidemiological studies (Landi et al., 2005). Identification of these factors may help to target specific interventions aimed to promote adequate physical function and, at the same time, prevent disability in late life. Fried and colleagues hypothesized the existence of a stage of pre-clinical disability in which there is a decrease in functional ability, and a greater risk of functional decline and disability but autonomy is still possible (Fried et al., 2001). The main aim of the ilSIRENTE study is to expand this knowledge and to verify whether this hypothesis can be applied also to a population of old–old people. Our study presents some limitations. First, the crosssectional design of the study does not allow to clarify any cause-effect mechanism. Second, although the MDS-HC is a standardized, comprehensive assessment instrument, the recording of pain is not its specific focus. Pain was assessed based on evaluation of the study physician, and the potential for over- or underestimation remains a concern, especially among those with difficulty communicating. In this context, we did not collect data on important pain characteristics, such as pain location which is a relevant determinant of physical functional limitations (Lichtenstein et al., 1998). Indeed, results on physical tests performed may widely vary depending on pain localization (i.e., hand or wrist pain for grip strength or lower extremity pain for physical performance battery). Despite the fact that we adjusted our analyses for many health and disease-related characteristics that are different between participants with and without pain, there could be unmeasured confounders that we cannot adjust for. Finally, potential inaccuracy in reporting clinical diagnoses may derive from the fact that they were assessed by a study physician and not based on specific criteria. In particular, osteoarthritis is often diagnosed to explain pain when another cause cannot be determined, while common soft tissue disorders such as myofascial pain and fibromyalgia are often underdiagnosed. Moreover, severity of osteoarthritis may widely vary, and a single variable may not capture the variability of this chronic condition. In conclusion, the present study shows that among old–old subjects living in the community, daily pain is highly prevalent and that this condition is associated
with impaired muscle strength and physical performance. These findings underscore the importance of optimizing pain control in this population.
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Association between daily pain and physical function among old–old adults living in the community: Results from the ilSIRENTE study Graziano Onder
b
a,*
, Matteo Cesari a,b, Andrea Russo a, Valentina Zamboni a, Roberto Bernabei a, Francesco Landi a
a Department of Gerontology, Catholic University of Sacred Heart, Rome, Italy Department of Aging and Geriatric Research, University of Florida, College of Medicine, Gainesville, FL, USA
Received 12 April 2005; received in revised form 18 November 2005; accepted 5 December 2005
Abstract Little is known about the impact of pain on physical function among old–old subjects. The aim of the present cross-sectional study was to assess the association of daily pain with muscle strength and physical performance in a population of subjects aged 80 or older living in the community. We used data from baseline evaluation of the ilSIRENTE Study. Muscle strength was measured by hand grip strength. Physical performance was assessed using the physical performance battery score, which is based on three timed tests: 4-m walking speed, balance, and chair stand tests. Daily pain was defined as any type of pain or discomfort in any part of the body manifested every day over the 7 days preceding the assessment. Mean age of 273 participants was 85.1 (SD 4.6) years, 181 (66.3%) were women and 150 (54.9%) reported daily pain. After adjustment for potential confounders, participants with daily pain had lower grip strength and physical performance battery score (indicating worse performance) than other participants (hand grip strength: daily pain 31.5 kg, SE 1.4, no daily pain 35.0, SE 1.1, p = 0.02; physical performance battery score: daily pain 6.5, SE 0.3, no daily pain 7.2, SE 0.3, p = 0.05). Both hand grip strength and physical performance battery score progressively declined as pain severity increased. In conclusion, the present study shows that among old–old subjects living in the community, daily pain is highly prevalent and that this condition is associated with impaired muscle strength and physical performance. Ó 2005 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. Keywords: Elderly; Physical performance; Muscle strength
1. Introduction Pain in the older population is a major health issue, both because of its high prevalence and impact on physical and psychological well being (Gureje et al., 1998). It has been estimated that in older populations, the prevalence of pain ranges from 45% to 80%, depending on age, setting, and country of residence (Bernabei et al., 1998; Landi et al., 2001; Thomas et al., 2004). In addi*
Corresponding author. Tel.: +39 06 30154341; fax: +39 06 3051911. E-mail address: [email protected] (G. Onder).
tion, this condition has been proved to interfere with daily activities, cause depression and emotional distress, leading to increased costs related to caregiver burden, long-term institutionalization, and physicians referral (Won et al., 1999; Lamb et al., 2000; Al Snih et al., 2001; Leveille et al., 2001; Reyes-Gibby et al., 2002; Weiner et al., 2004; Onder et al., 2005a). Despite these considerations, physicians frequently fail to accurately diagnose and treat pain, particularly among older adults: it has been shown that independently of clinical setting and clinical diagnoses, one-quarter of older adults with pain does not receive any analgesic drugs and those older than 85 years are even less likely
0304-3959/$20.00 Ó 2005 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.pain.2005.12.003
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to receive any treatment (Bernabei et al., 1998; Landi et al., 2001). These data, along with the emphasis on pain as the fifth vital sign by the Veteran’s Administration and the attention on pain assessment by Joint Commission on Accreditation of Healthcare Organization, highlight the importance of a better assessment of pain and its correlates, particularly among old–old subjects, that represent a progressively growing population often not adequately represented in epidemiological studies (Health agencies update, 1999; Joint Commission on Accreditation of Health Care Organizations, 2000). In this context, little is known about the impact of pain on physical function among old–old subjects. Therefore, the aim of the present cross-sectional study was to assess the association of pain with muscle strength and physical performance in a population of subjects aged 80 or older living in the community. 2. Methods The ilSIRENTE study is a prospective cohort study performed in the mountain community living in the Sirente geographic area (L’Aquila, Abruzzo) in Central Italy. This study was designed by the Department of Gerontology of the Catholic University of Sacred Heart (Rome, Italy) and developed by the teaching nursing home Opera Santa Maria della Pace (Fontecchio, L’Aquila, Italy) in a partnership with local administrators and primary care physicians of Sirente Mountain Community Municipalities. All the participants signed an informed consent at the baseline visit. Details of the ilSIRENTE study protocol are described elsewhere (Landi et al., 2005). 2.1. Study population A preliminary list of all community dwelling older adults living in the Sirente area was obtained at the end of October 2003 from the Registry Offices of the 13 municipalities involved in the study. From this preliminary list, potential study participants were identified by selecting all persons born before January 1st, 1924 living in the Sirente area. Of the initial 514 subjects screened, 32 men and 53 women died or moved away from the area before the baseline assessment. Among those eligible (n = 429), prevalence of refusals was very low (16%). Subjects participating in the study did not differ significantly from those who refused to participate by age and gender. As a result, the overall sample population enrolled in the ilSIRENTE study consisted of 364 subjects. 2.2. Data collection Baseline participants’ assessments began in December 2003 and were completed in September 2004. Assessors were trained on how to perform each component of the ilSIRENTE study protocol. The Minimum Data Set for Home Care (MDSHC) form was administered to all study participants, following the guidelines published in the MDS-HC manual (Morris et al., 1996, 1997). The MDS-HC contains over 350 data elements including socio-demographics, physical and cognitive
status variables, as well as major clinical diagnoses (Morris et al., 1996). Moreover, the MDS-HC also includes information about an extensive array of signs, symptoms, syndromes, and treatments (Morris et al., 1996). Clinical diagnoses were recorded by a study physician gathering information from the patient, the general practitioner and after physical examination, careful review of patient clinical documentation (including laboratory tests and X-rays) and based on previous medical history. The cognitive performance scale (CPS) was used to assess cognitive status (Hawes et al., 1995). The CPS has shown an excellent inter-rater and test–retest reliability when completed by nurses performing usual assessment duties (Hawes et al., 1995; Landi et al., 2000). The CPS score ranges from 0 (intact cognition) to 6 (severe dementia). We categorized cognitive status as follows: normal (CPS score of 0–1), moderately impaired (CPS score of 2–4), and severely impaired (CPS score of 5–6). The depression rating scale was used to assess the presence of depressive symptoms (Burrows et al., 2000). Based on a previous observation, participants with a score P3 were diagnosed as depressed. The depression rating scale has proven reliable for detecting depression among older adults (Burrows et al., 2000). Participants reporting light intensity (aerobic) exercise performed for at least 2–4 h per week during the last year were defined physically active. Activities of daily living (ADL) considered for this study were dressing, eating, toilet use, bathing, mobility in bed, locomotion, and transfer. Impairment in each ADL was defined as the need of assistance to complete the task. Data on medications taken in 7 days prior to the assessment were also collected and coded according to the Anatomical Therapeutic and Chemical codes (Pahor et al., 1994). Analgesics were classified into three different groups according to the WHO 3-step ladder, including nonopioids (level 1; e.g., salicylates and nonsteroidal anti-inflammatory drugs), weak opioids (level 2; e.g., codeine phosphate, pentazocine hydrochloride, and buprenorphine hydrochloride), and strong opioids (level 3; e.g., morphine sulfate, hydromorphone hydrochloride, fentanyl citrate, and methadone hydrochloride). 2.3. Assessment of pain Pain was defined as any type of pain or discomfort in any part of the body that was manifested over the 7 days preceding the assessment (Morris et al., 1996). As part of the standard MDS assessment, the study physician was instructed to ask simple and direct questions about whether the participant experienced pain. Among participants unable to talk or lacking the ability to adequately describe symptoms, the assessors were also instructed to observe for indicators of pain, including moaning, crying, wincing, frowning, other facial expressions or posturing such as guarding or protecting an area of the body. Pain frequency was coded as less than daily, daily with a single episode or daily with multiple episodes. To avoid misclassification of pain, subjects with cognitive impairment, defined as CPS score P2, were excluded from the study (n = 91). For the purpose of this study we compared subjects experiencing ‘daily pain’ (n = 150) with those experiencing pain less than daily or without pain (‘no daily pain’ n = 123). Pain severity was coded as mild, moderate, severe or excruciating; number of painful sites was coded as single or multiple. Datum on sites
G. Onder et al. / Pain 121 (2006) 53–59
with pain was missing for one participant. Independent, dual assessment of pain items (including presence of pain, pain frequency, severity, and number of sites with pain) in a diverse sample of patients during testing and revision of the MDS showed an average weighted Kappa exceeding 0.7 (Morris et al., 1997). 2.4. Outcome measures Physical performance battery – Physical performance was assessed by the physical performance battery score. This latter is composed by three timed tests: 4-m walking speed, balance, and chair stand tests. Timed results from each test were rescored from 0 (worst performers) to 4 (best performers). The sum of the results from the three categorized tests (ranging from 0 to 12) was used for the present analyses (Guralnik et al., 1995; Onder et al., 2002). Categorization of results from 4-m walking speed and chair stand tests was obtained on the basis of the ilSIRENTE population-specific quartiles. The balance test was categorized according to previously established cut-points provided by Guralnik et al. (1995). Muscle strength measure – Grip strength was used as an indicator of muscle strength. Grip strength was known to be positively correlated with lower extremity strength and performance in older persons (Era et al., 1992; Rantanen et al., 1994; Visser et al., 2000) and this measure has shown to be predictive of major health-related events in older persons; (Rantanen et al., 1999; Al Snih et al., 2004). Moreover, grip strength is a reliable and portable muscle strength test that can be administered in a home setting (Al Snih et al., 2004). Grip strength was assessed by hand grip strength measured by a dynamometer. 2.5. Statistical analysis To avoid misclassification of pain, from the initial sample of 364 participants, we excluded 91 subjects with cognitive impairment, defined as CPS score P2. In the remaining sample, differences in proportions and means of covariates between participants with (n = 150) and without daily pain (n = 123) were assessed using Fisher’s Exact Test and t test statistics, respectively. Analysis of covariance (ANCOVA) was used to calculate adjusted means of hand grip strength and physical performance battery score according to presence of daily pain, pain severity, and number of sites with pain. Variables considered for adjustment were those associated with daily pain at p 6 0.10 at the univariate analysis and those thought to be clinically significant. Final analyses were adjusted for age, gender, cognitive performance scale score, osteoarthritis, depression, physical activity, and body mass index. All analyses were performed using SPSS software (version 9.0, SPSS Inc., Chicago, IL).
3. Results Mean age of 273 subjects participating the study was 85.1 (SD 4.6) years, and 181 (66.3%) were women. Of the total sample, 150 subjects (54.9%) presented with daily pain; 110 subjects (40.3%) defined daily pain as mild or moderate and 40 (14.7%) severe or excruciating.
55
Daily pain was limited to a single site in 24 cases (8.8%) and involved multiple sites in 125 cases (45.8%). Characteristics of the study population according to the presence of daily pain are summarized in Table 1. Compared with participants without daily pain, those with daily pain were younger, more likely to be women, and had higher prevalence of osteoarthritis and depression. No significant difference between the two study groups was observed for other medical conditions. In addition, subjects with daily pain tended to be less physically active and to have a higher body mass index, compared with other participants. Only 39 participants (26%) reporting daily pain and 9 (7.3%) not reporting daily pain were using pain medications; overall 44 were receiving NSAIDs or acetaminophen (WHO level 1) and 5 weak or strong opiates (WHO levels 2 and 3). In the daily pain group, use of pain medications increased as severity and number of sites with pain increased. Participants with daily pain had significant lower grip strength and physical performance battery score (indicating worse performance) than other participants (hand grip strength: daily pain 29.8 kg, SE 1.0, no daily pain 37.3, SE 1.3, p < 0.001; physical performance battery score: daily pain 6.9, SE 0.3, no daily pain 8.4, SE 0.3, p < 0.001). After adjustment for potential confounders, which included age, gender, cognitive performance scale score, osteoarthritis, depression, physical activity, and body mass index, these associations were still consistent (hand grip strength: daily pain 31.5 kg, SE 1.4, no daily pain 35.0, SE 1.1, p = 0.02; physical performance battery score: daily pain 6.5, SE 0.3, no daily pain 7.2, SE 0.3, p = 0.05). Figs. 1 and 2 report the associations of the outcome measures with pain severity and number of painful sites. As pain severity increased both hand grip strength and physical performance battery score progressively declined (p for trend 0.06 and 0.07, respectively, Fig. 1). Examining the association between these measures and number of sites with pain, we observed a borderline significant trend for hand grip strength (p for trend 0.05) but not for physical performance battery score (p for trend 0.15, Fig. 2). In the fully adjusted models, no significant interaction between gender and pain severity or number of sites with pain was observed. 4. Discussion This is one of the first studies to assess the association of daily pain with physical function among old–old subjects living in the community. We show that daily pain is associated with impaired physical performance and muscle strength, irrespective of potential confounders and that this association gets stronger as pain severity increases. In addition, the association of pain and
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Table 1 Characteristics of study population according to presence of daily pain Characteristics
No daily pain n = 123 (%)
Daily pain n = 150 (%)
P
Age, years (mean ± SD)
85.4 ± 4.9
84.9 ± 4.3
0.37
Female gender
64 (52.0)
117 (78)
<.001
Living alone
48 (39.3)
57 (38.0)
0.82
Cognitive Performance Scale score 0 1
104 (84.6) 19 (15.4)
127 (84.7) 23 (15.3)
Number of impaired ADL (mean ± SD)
0.48 ± 1.55
0.78 ± 1.71
0.13
Diseases Ischemic heart disease Congestive heart failure Hypertension Peripheral vascular disease Stroke Diabetes Chronic obstructive pulmonary disease Parkinson’s disease Cancer Osteoarthritis Depressiona
15 (12.2) 6 (4.9) 94 (76.4) 5 (4.1) 2 (1.6) 29 (23.6) 14 (11.4) 0 (0) 6 (4.9) 10 (8.1) 18 (14.6)
19 (12.7) 7 (4.7) 114 (76.0) 4 (2.7) 4 (2.7) 38 (25.3) 25 (16.7) 4 (2.7) 8 (5.3) 41 (27.3) 49 (32.7)
0.91 0.94 0.94 0.52 0.69 0.74 0.21 0.13 0.87 <.001 0.001
Physical activityb
98 (79.7)
93 (62.8)
0.002
Body mass index, kg/m (mean ± SD)
25.6 ± 3.5
26.2 ± 4.7
0.21
Use of Benzodiazepines Statins Ace inhibitors
9 (7.3) 7 (5.7) 52 (42.3)
17 (11.3) 12 (8.0) 55 (36.7)
0.26 0.46 0.35
2
a b
0.98
Defined as MDS Depression Rating Scale P3. Participants reporting light intensity (aerobic) exercise performed for at least 2–4 h per week during the last year.
muscle strength becomes progressively more pronounced as number of sites with pain increases. Pain may impact on physical function as a consequence of a reduced range of joint movement or reflex inhibition of skeletal muscles, resulting in muscle weakness and impaired strength and physical performance (Young, 1993). Alternatively, pain may limit physical activity and consequently determine a gradual reduction in physical function. Finally, it cannot be excluded that muscle weakness and impaired physical function are directly consequence of medical conditions of late life which are also associated with pain. However, these latter hypotheses are made unlikely by the fact that we adjusted the analyses for indicators of physical activity and comorbid conditions. Results of this study underline the importance of careful assessment of pain when examination of physical function and disability is performed (Flaherty, 2001). Evaluation of pain is easy to perform, relatively cost free, and it can provide precious information: Engle and colleagues have shown that assessment of pain by nursing assistants is unbiased and as accurate as higher-trained medical personnel (Engle et al., 2001). Al Snih and colleagues have proved that asking one simple ques-
tion about presence of pain and discomfort by research assistants who may not have had a medical background may help to predict future disability (Al Snih et al., 2001). These data, along with the observation that pain may impact on physical function and that appropriate pain management results in quicker clinical recovery, shorter hospital stays, fewer readmissions, and improved quality of life (Phillips, 2000), suggest that the assessment and treatment of this condition is extremely rewarding not only for the patients, but also from a health care system prospective. Unfortunately, despite the World Health Organization indicating that almost all patients with malignant pain can be adequately treated by means of simple oral regimens that usually do not produce adverse effects (Stjernsward, 1988), and that non-malignant pain can be effectively managed with both nonpharmacologic and pharmacologic approaches (Blumstein and Gorevic, 2005), these conditions are largely undertreated, particularly in the old–old subjects. In particular, in our study only one-fourth of participants reporting daily pain received pain medications. This result is in line with a previous observation conducted among older adults living in the community in Italy (Landi et al., 2001). However, independently of
G. Onder et al. / Pain 121 (2006) 53–59
30
20
10
30
20
10
0
0 No daily pain (n=123)
p for trend = 0.06
Mild-Moderate (n=110)
6
4
2
0 No daily pain (n=123)
p for trend = 0.07
p for trend = 0.05
Severity of daily pain
p=0.03
8
No daily pain (n=123)
SevereExcruciating (n=40)
Physical Performance Battery score
Physical Performance Battery score
p=0.02
p=0.02
Hand Grip Strength (kg)
Hand Grip Strength (kg)
40
p=0.11
40
57
Mild-Moderate (n=110)
SevereExcruciating (n=40)
Severity of daily pain
Fig. 1. Adjusted means (standard errors) of hand grip strength and physical performance battery score according to severity of daily pain. Analyses are adjusted for age, gender, cognitive performance scale score, osteoarthritis, depression, physical activity, and body mass index.
setting, country, and patients’ characteristics pain is widely undertreated in old populations, and advanced aged seems to reduce the probability to receive adequate analgesic treatment (Bernabei et al., 1998; Won et al., 2004). To assess the effect of pain on physical function, we used the hand grip strength and the physical performance battery score. These two measures of physical function provide a ‘‘multidimensional’’, objective and standardized assessment of older persons, they are able to characterize community dwelling older people across a broad spectrum of functional status and they are sensitive to changes over time (Guralnik et al., 1989, 1994; Onder et al., 2002). In addition, several studies indicated that physical performance measures can complement self-reported measures in the assessment of older persons’ functional status, as suggested by the fact that they tap different, but important, dimensions of physical function (Reuben et al., 1995; Simonsick et al., 2001).
8
Single site (n=24)
Multiple sites (n=125)
Sites with daily pain
p=0.08
6
4
2
0 No daily pain (n=123)
p for trend = 0.15
Single site (n=24)
Multiple sites (n=125)
Sites with daily pain
Fig. 2. Adjusted means (standard errors) of hand grip strength and physical performance battery score according to sites with daily pain. Datum on sites with pain was missing for one participant. Analyses are adjusted for age, gender, cognitive performance scale score, osteoarthritis, depression, physical activity, and body mass index.
In this study, we used grip strength as an indicator of general strength. Although being a direct measure of hand strength, grip strength has frequently been used as an overall measure of body strength, because it is a reliable and portable strength test that can be administered in a home setting (Al Snih et al., 2004). Grip strength in older persons was related to arm flexion (reported correlation coefficients between 0.57 and 0.65), knee extension (0.47–0.51), trunk extension (0.33–0.56), and trunk flexion strength (Era et al., 1992; Rantanen et al., 1994). Physical function measures have gained increased acceptance and use for the clinical evaluation of older persons. In addition, it has been consistently demonstrated that measures of physical function can predict major health-related outcomes in the elderly, such as disability, death, and institutionalization (Guralnik
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et al., 1989, 1995; Rantanen et al., 1999; Al Snih et al., 2004; Onder et al., 2005b). For these reasons, adding an evaluation of physical function to the traditional clinical examination is particularly important in the assessment of older persons. However, the use of such tests in the clinical setting has not been widely adopted possibly owing to the misperception that they often require substantial space, special equipment, or are unduly time consuming. The ilSIRENTE study offers a unique opportunity to investigate factors associated with impaired physical function among old–old and frail subjects, which frequently are excluded from epidemiological studies (Landi et al., 2005). Identification of these factors may help to target specific interventions aimed to promote adequate physical function and, at the same time, prevent disability in late life. Fried and colleagues hypothesized the existence of a stage of pre-clinical disability in which there is a decrease in functional ability, and a greater risk of functional decline and disability but autonomy is still possible (Fried et al., 2001). The main aim of the ilSIRENTE study is to expand this knowledge and to verify whether this hypothesis can be applied also to a population of old–old people. Our study presents some limitations. First, the crosssectional design of the study does not allow to clarify any cause-effect mechanism. Second, although the MDS-HC is a standardized, comprehensive assessment instrument, the recording of pain is not its specific focus. Pain was assessed based on evaluation of the study physician, and the potential for over- or underestimation remains a concern, especially among those with difficulty communicating. In this context, we did not collect data on important pain characteristics, such as pain location which is a relevant determinant of physical functional limitations (Lichtenstein et al., 1998). Indeed, results on physical tests performed may widely vary depending on pain localization (i.e., hand or wrist pain for grip strength or lower extremity pain for physical performance battery). Despite the fact that we adjusted our analyses for many health and disease-related characteristics that are different between participants with and without pain, there could be unmeasured confounders that we cannot adjust for. Finally, potential inaccuracy in reporting clinical diagnoses may derive from the fact that they were assessed by a study physician and not based on specific criteria. In particular, osteoarthritis is often diagnosed to explain pain when another cause cannot be determined, while common soft tissue disorders such as myofascial pain and fibromyalgia are often underdiagnosed. Moreover, severity of osteoarthritis may widely vary, and a single variable may not capture the variability of this chronic condition. In conclusion, the present study shows that among old–old subjects living in the community, daily pain is highly prevalent and that this condition is associated
with impaired muscle strength and physical performance. These findings underscore the importance of optimizing pain control in this population.
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