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Relationship of Back and Neck Pain With Quality of Life in the Croatian General Population
ORIGINAL ARTICLES RELATIONSHIP OF BACK AND NECK PAIN WITH QUALITY OF LIFE IN THE CROATIAN GENERAL POPULATION Zeljko Pedisic, PhD, a, b Shelly Pranic, MBiol, c and Danijel Jurakic, PhD d
ABSTRACT Objective: The purpose of this study was to determine the prevalence of back pain and neck pain and their relationship with the quality of life in the Croatian general population. Methods: This was a cross-sectional study using home-based face-to-face interviews of 1030 participants (51.6% females) 15 years or older. Back and neck pain frequencies were assessed using single items and quality of life using the Short Form Survey and Satisfaction with Life Scale. Analysis of covariance was conducted, where back pain or neck pain frequency was used as the categorical predictor; physical component summary or mental component summary, as the dependent variable; and age, body mass index, and physical activity level, as covariates. Results: The prevalence of back pain was 66.3% (95% confidence interval [CI], 62.3%-70.3%) and 62.9% (95% CI, 58.7%-67.2%) in females and males, respectively. The prevalence of neck pain was 58.0% (95% CI, 53.8%-62.2%) for females and 53.6 (95% CI, 49.2%-58.0%) for males. Differences between men and women were not significant (P N .05). Adjusted mean values for physical component summary and mental component summary were substantially lower in participants who reported back or neck pain often/almost always compared with those without pain. Differences ranged from 8.11 to 11.86 points (95% CI, 5.54-13.99) and from 9.61 to 10.99 points (95% CI, 7.3513.45) in females and males, respectively. Conclusions: The findings of this study showed that back and neck pain are highly prevalent and negatively related to quality of life in the Croatian general population. These data might raise the awareness of local government health authorities and lead to improvements in health care service for people with back and neck pain. (J Manipulative Physiol Ther 2013;36:267-275) Key Indexing Terms: Low Back Pain; Neck Pain; Chronic Pain; Quality of Life; Personal Satisfaction
ack and neck pain are growing public health problems. As many as 80% of adults experience back pain in their lifetime according to the World Health Organization. 1 The lifetime prevalence of neck pain for adults across different countries has been reported to range from 14.2% to 71.0%, with a 48.5% mean. 2 Evidence suggests that the prevalence of back and neck
B a
Researcher, Institute of Sport Science, Karl-Franzens-University of Graz, Graz, Austria. b Researcher/Lecturer, Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia. c Researcher/Lecturer, School of Medicine, University of Split, Split, Croatia. d Researcher/Lecturer, Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia. Submit requests for reprints to: Zeljko Pedisic, PhD, Researcher/Lecturer, Horvacanski zavoj 15, HR-10000 Zagreb, Croatia (e-mail: [email protected]). Paper submitted October 31, 2012; in revised form March 9, 2013; accepted March 25, 2013. 0161-4754/$36.00 Copyright © 2013 by National University of Health Sciences. http://dx.doi.org/10.1016/j.jmpt.2013.05.012
pain is high even in children and adolescents. 2,3 Consequences of these conditions include economic burden, 4-6 disability, 7,8 occupational absenteeism, 9,10 and diminished work capacity. 6,11 Moreover, in studies examining pain in various regions of the spine, the overall prevalence rates are highest for low back pain followed by neck pain and mid back pain. 8,12,13 It has also been observed that women are more likely to experience back and neck pain. 2,12-16 Several studies have described the relationship of either back or neck pain with health-related quality of life (HRQoL). Most of them were conducted on different general adult populations 15,17-20 or patients with chronic back pain 21-25 and fewer on other populations such as schoolchildren 26 and elderly. 27 Despite of the valuable data from several studies, evidence on the relationship of back or neck pain with HRQoL in general population is still scarce, whereas methodological differences of the studies preclude drawing final conclusions. Furthermore, somewhat less attention has been given to the relationship between back or neck pain and life satisfaction. It has been studied in a working population 28 and in people with whiplashassociated disorders, 29,30 but, to the best of our knowledge, 267
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evidence collected from representative samples of the general population is still lacking. Little is known about the quality-of-life outcomes of back and neck pain in Croatia. Braš et al 31 investigated HRQoL in Croatian war veterans with posttraumatic stress disorder and low back pain, and Jajić et al 32 described the relationship between spinal pain and HRQoL in patients with ankylosing spondylitis and psoriatic arthritis. However, no recent studies have examined the prevalence of back/ neck pain or its relationship with the quality of life in the Croatian general population. Insight into these data might raise the awareness of local and regional government health authorities and lead to improvements in health care service for people with back and neck pain. Furthermore, it might motivate administrative bodies in primary care to initiate systematic monitoring of body posture and other factors, which may lead to the incidence of back and neck pain, especially nowadays when simple and affordable screening methods are available. 33,34 Besides, it might help patients, physicians, and allied health professionals better understand possible nonclinical benefits of back or neck pain treatment. Therefore, the purpose of this study was to determine the prevalence of back and neck pain and examine the relationship of these conditions with HRQoL and life satisfaction in the Croatian general population.
METHODS Subjects A cross-sectional study was conducted in November 2007 on a stratified random sample of 1076 Croatian inhabitants 15 years or older. Participants were interviewed face to face in their households. Unfortunately, no exact data on the response rate are available for the current study. Nevertheless, the survey company in charge of the sample selection and data collection indicated that the common response rate in similar household surveys that they regularly conduct in Croatia is approximately 35%. Sample stratification was performed by settlement size and geographical region using data from the Croatian 2001 census. At first, we randomly selected households. In each selected household, interviewers performed the random selection of 1 resident. The only eligibility criterion was that the selected resident is 15 years or older. A detailed description of the sample design can be found elsewhere. 35 Adult subjects gave written informed consent before being interviewed. Written consent was obtained from a parent or guardian after adolescent assent. To assure the anonymity of participants, upon completion of the interview, each questionnaire was sealed in an envelope with a barcode as the unique identifier. The identity of the participants was kept confidential and remained unknown to the researchers. The study protocol was approved by the Institutional Review Board at the Faculty of Kinesiology, University of Zagreb. All participants consented to participate in this study.
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Table 1. Sample characteristics x̄ ± s/% a Variable/category
Females
Males
Age (y) Size of settlement b b2000 2001-10 000 10 001-100 000 N100 000 Level of education Primary school Secondary school Undergraduate degree Graduate degree Postgraduate degree Household income per capita (€) BMI (kg/m2) b16.0 16.0-18.5 18.5-25 25-30 N 30
39.31 ± 14.97
38.99 ± 14.76
36.7 14.3 19.8 29.2
40.6 15.5 19.7 24.1
15.4 61.2 12.7 10.4 0.4 362.37 ± 253.72 24.00 ± 4.22 0.4 4.2 62.2 23.0 10.3
9.8 65.4 12.6 11.0 1.2 363.12 ± 216.38 26.23 ± 3.63 0.0 0.4 40.7 44.3 14.6
BMI, body mass index. a Mean ± SD (for quantitative variables)/percentages (for categories). b Number of inhabitants.
Because of incomplete data, 4.3% of the subjects were subsequently excluded from the study. The final sample consisted of 1030 subjects (51.6% females; mean age, 39.16 ± 14.86 years). The study sample is considered representative for the population of Croatian citizens 15 years or older. According to the Croatian 2011 census, there are somewhat more than 3.6 million Croatian inhabitants of the aforementioned age. General characteristics of the sample are presented in Table 1. Power analysis indicated that our sample size was large enough to detect significant differences at P b .05 using the analysis of covariance (ANCOVA) with an acceptable power of 0.77, if the true effect size in the population was at least small (F ≥ 0.10), according to Cohen. 36
Measures Frequency of back and neck pain was assessed using 2 separate questions (“How often have you recently experienced back pain?” and “How often have you recently experienced neck pain?”) with 5 possible answers: never, seldom, sometimes, often, and always. One-month testretest reliability of the questions was satisfactory (intraclass correlation coefficient, 0.53 for back pain and 0.49 for neck pain). Health-related quality of life was assessed using the Short-Form Health Survey (SF-36). 37 The questionnaire consists of 36 items that measure 8 dimensions of HRQoL: physical functioning, role physical, bodily pain, general health, vitality, social functioning, role emotional, and mental health. The aforementioned dimensions form 2 summary measures: physical component summary score
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(PCS) and mental component summary score (MCS). Physical component summary correlates most highly to the physical component scales (physical functioning, role physical, and bodily pain) and MCS to the mental component scales (social functioning, role emotional, and mental health). 38 General health, vitality, and social functioning share variance evenly with both summary measures. 38 Higher scores on SF-36 variables indicate a higher HRQoL. Previous studies have shown high reliability and validity of the Croatian version of SF-36 (internal consistency reliability range from 0.78 to 0.94). 39 Life satisfaction, which is viewed as people's perception of the difference between their reality and their aspirations and goals, was assessed using the Satisfaction with Life Scale (SWLS). 40 The questionnaire consists of five 5-point Likert scale items. The overall life satisfaction score was calculated as the arithmetic mean of all items. A higher score indicates higher life satisfaction and vice versa. Previous studies have shown high reliability (internal consistency reliability range from 0.79 to 0.89) and the single-factor structure of SWLS items. 40-42 In addition, we collected data on potential confounding variables: sex, age, body mass index (BMI), and physical activity level, as previous studies have shown their significant relation to HRQoL 43-45 and life satisfaction 46-48 in general population. Body mass index was calculated as weight/ height 2 (kilogram per square meter), according to the selfreported body weight and height. Total physical activity level was estimated in MET (metabolic equivalency of task)hours/week using the long version of the International Physical Activity Questionnaire (IPAQ), 49 which has shown satisfactory measurement properties in the Croatian general population. 50 Because of survey data availability, we did not consider including other potential confounding variables.
Pedisic, Pranic, and Jurakic Back and Neck Pain and Quality of Life
Table 2. Frequency of back and neck pain in Croatian general population RF, % (95% CI) Variable/category Back pain frequency Never Seldom Sometimes Often Almost always Neck pain frequency Never Rarely Sometimes Often Almost always
Females
Males
Pa
33.7 (29.7-37.7) 25.0 (21.4-28.7) 27.1 (23.3-30.9) 10.5 (7.9-13.2) 3.6 (2.0-5.2)
37.1 (32.8-41.3) 26.4 (22.5-30.3) 24.4 (20.6-28.2) 10.1 (7.4-12.7) 2.0 (0.8-3.3)
.257 .617 .319 .806 .131
42.0 (37.8-46.2) 23.9 (20.3-27.5) 22.4 (18.9-26.0) 9.0 (6.6-11.5) 2.6 (1.3-4.0)
46.4 (42.0-50.8) 23.6 (19.9-27.3) 21.0 (17.4-24.6) 7.5 (5.1-9.8) 1.6 (0.5-2.7)
.158 .902 .575 .358 .258
CI, confidence interval; RF, relative frequency. a P value for the difference between females and males.
between back and neck pain groups using series of ANCOVAs. Back or neck pain frequency was used as the categorical predictor; PCS or MCS, as the dependent variable; and age, BMI, and physical activity level, as covariates. Categories “often” and “almost always” according to back/ neck pain frequency were merged because of a low number of participants reporting pain almost always (1.6%-3.6%). To evaluate group-to-group differences, ANCOVA was followed by a post hoc test. Because sex has shown to be a strong determinant of HRQoL 45 and life satisfaction, 47 all analyses were conducted separately for females and males. Correlations and differences were considered statistically significant at a P b .05. Before significance testing, P values were adjusted for multiple significance tests using the Bonferroni correction.
RESULTS Data Analysis Data analyses were performed with IBM SPSS Statistics 19 (SPSS, Inc, an IBM Company, Chicago, IL). Although we used an automated data entry system using optical scanning, before analysis digital data were manually checked for errors. Data were screened for outliers and processed according to the SF-36 manual 51 and IPAQ scoring protocol. 52 Demographic and lifestyle variables are presented using mean ± SD. The prevalence rates of back and neck pain were expressed by percentages and the respective 95% confidence intervals (CIs). The prevalence rates in females and males were compared using the two-proportion z-test. Because most of the variables were not normally distributed, the relationship of back pain and neck pain with quality of life and life satisfaction was determined using partial Spearman rank correlation coefficients. Correlations were adjusted for age, BMI, and physical activity level. Normal distributions of PCS and MCS allowed us to explore differences in HRQoL
Prevalence of Back and Neck Pain The prevalence of back pain was 66.3% (95% CI, 62.3%70.3%) and 62.9% (95% CI, 58.7%-67.2%) in females and males, respectively (Table 2). The prevalence of neck pain was 58.0% (95% CI, 53.8%-62.2%) for females and 53.6 (95% CI, 49.2%-58.0%) for males. Around 80% of the participants who experienced back pain reported it as occurring rarely or sometimes. A similar percentage was determined for the participants experiencing neck pain rarely or sometimes. A frequent back or neck pain was much less prevalent. Differences between men and women in overall prevalence of back and neck pain were not significant (P = .26 for back pain and P = .16 for neck pain).
Correlation of Back and Neck Pain With HRQoL and Life Satisfaction All dimensions of HRQoL were significantly negatively correlated to back and neck pain in both females and males (P b .001) (Table 3). Notably, moderate correlations were
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Table 3. Relationship of back pain and neck pain with HRQoL and life satisfaction Females, r a (P) b
Males, r a (P) b
Quality of life variable
Back pain
Neck pain
Back pain
Neck pain
Physical functioning Role physical Bodily pain General health Vitality Social functioning Role emotional Mental health PCS MCS Life satisfaction
− 0.23 (b.001) − 0.32 (b.001) − 0.41 (b.001) − 0.33 (b.001) − 0.27 (b.001) − 0.37 (b.001) − 0.25 (b.001) − 0.25 (b.001) − 0.33 (b.001) − 0.29 (b.001) − 0.17 (.007)
− 0.26 (b.001) − 0.33 (b.001) − 0.47 (b.001) − 0.38 (b.001) − 0.23 (b.001) − 0.42 (b.001) − 0.28 (b.001) − 0.21 (b.001) − 0.42 (b.001) − 0.26 (b.001) − 0.13 (.212)
− 0.28 (b.001) − 0.24 (b.001) − 0.47 (b.001) − 0.37 (b.001) − 0.38 (b.001) − 0.43 (b.001) − 0.26 (b.001) − 0.32 (b.001) − 0.38 (b.001) − 0.34 (b.001) − 0.16 (.050)
− 0.27 (b .001) − 0.29 (b.001) − 0.43 (b.001) − 0.33 (b.001) − 0.38 (b.001) − 0.44 (b.001) − 0.24 (b.001) − 0.34 (b.001) − 0.35 (b.001) − 0.38 (b.001) − 0.15 (.077)
MCS, mental component summary score; PCS, physical component summary score. a Spearman rank correlation adjusted for age, BMI, and physical activity level. b Bonferroni-adjusted P value.
found for bodily pain, general health, social functioning, and PCS for both sexes. Moderate correlations were also found for role physical in females and for vitality, mental health, and MCS in males. Correlations with other HRQoL dimensions were low. Shared variance, calculated as squared correlation, between back and neck pain and HRQoL variables ranged from 4.4% to 22.1% and 5.8% to 22.1% in females and males, respectively. Life satisfaction was poorly correlated with back and neck pain in both females and males. The only significant correlation with life satisfaction was found for back pain in females.
Differences in HRQoL According to Back and Neck Pain Frequency All overall between-group differences in PCS and MCS using ANCOVAs were significant (P b .001) (Figs 1A-D and 2A-D). Among females, medium effect sizes according to Cohen 36 were found for differences between back pain groups in PCS (η 2 = 0.12) and MCS (η 2 = 0.08) and between neck pain groups in MCS (η 2 = 0.08). In the male sample, medium effect sizes were determined for differences between back pain groups in PCS (η 2 = 0.13) and between neck pain groups also in PCS (η 2 = 0.12). Comparisons of back and neck pain groups in MCS showed large effect sizes. Namely, both respective partial η 2 were 0.15. The analysis of differences between neck pain groups in PCS among females revealed the largest effect size among all comparisons (η 2 = 0.20). Post hoc analysis showed that most of the nearby groups had not differed significantly. Significant differences between adjusted mean values of nearby groups ranged from 2.35 to 6.35 (95% CI, 0.53-8.57) among females and from 3.05 to 5.47 (95% CI, 1.31-8.50) among males. Conversely, all comparisons of nonadjacent groups (never vs sometimes and rarely vs often/almost always), which are separated from each other by 1 category, and opposite groups (never vs often/almost always) resulted in significant differences (P b .001). Mean differences between nonadjacent groups
ranged from 4.08 to 9.51 (95% CI, 2.33-11.80) and 4.08 to 8.46 (95% CI, 2.28-11.01) among females and males, respectively. Differences between opposite groups were between 8.11 and 11.86 (95% CI, 5.54-13.99) in females and between 9.61 and 10.99 (95% CI, 7.35-13.45) in males.
DISCUSSION Prevalence of Back and Neck Pain Our study revealed a high prevalence of both back and neck pain in the Croatian adult population. When compared with other countries, Croatia would be placed among 10% with the highest prevalence of back pain, 16 and it would rank similarly high in regard to the prevalence of neck pain. 53 However, because of a methodological heterogeneity across previous studies, 16,53 these conclusions should be taken with caution. Inconsistent with other studies in which women generally reported the occurrence of back and neck pain more frequently than men, 2,12-16 we did not find significant differences between sexes. This might be due to real differences between Croatian and other survey populations but also due to discrepancy from other studies in the pain questionnaire used.
Relationship of Back and Neck Pain With HRQoL We found a significant relationship between back and neck pain and all HRQoL dimensions after adjustment for age, BMI, and physical activity level. Low to moderate correlations between back and neck pain and HRQoL were found in both females and males. The highest correlations were determined with bodily pain and social functioning scales. A large proportion of variance of back and neck pain shared with bodily pain (16.8%-22.1%) was expected due to the obvious contextual overlap in respective questionnaire items. In SF-36, bodily pain scale is assessed using following questions: “How much physical pain have you had during the past 4 weeks?” and “During the past 4
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Pedisic, Pranic, and Jurakic Back and Neck Pain and Quality of Life
Fig 1. Differences in health-related quality according to back and neck pain frequency among females. A, Differences in PCS according to back pain frequency. B, Differences in PCS according to neck pain frequency. C, Differences in MCS according to back pain frequency. D, Differences in MCS according to neck pain frequency. *Category including participants who reported experiencing pain often or almost always. Bars denote mean values adjusted for age, BMI, and physical activity level, and whiskers denote their 95% CIs. weeks, how much did pain interfere with your normal work?” It might be assumed that the participants experiencing back or neck pain were more likely to have worse scores on the bodily pain scale. Although it might also be that the relationship between these characteristics is bidirectional or even directed from bodily pain to back and neck pain frequency only, we believe that these are less possible explanations of the correlation. Furthermore, a high percentage of shared variance between back/neck pain and social functioning (13.7%-19.4%) was an expected finding, too. The social functioning items of SF-36 ask participant about time and extent in which physical health or emotional problems interfered with his/her social activities (like visiting friends, relatives, etc). Although we cannot conclude the causality of the relationship between back and neck and social functioning scales, our results suggest that people with back or neck pain are limited in attending social activities and events, which is congruent with previous findings. 54,55 Negative relationship of back/neck pain with physical functioning, role physical, and PCS is also in accordance with the results of previous studies. 20,21,25 It has been shown that back and neck pain reduce physical activity 56 and working
capacity 6,11 and cause disability 7,8 and occupational absenteeism. 9,10 All of the aforementioned consequences of back/neck pain are likely to be direct causes of diminished scores in physical dimensions of HRQoL. The magnitude of relationship between back and neck pain and HRQoL variables should be considered in the context of the complexity of HRQoL, that is, its dependence on a wide variety of health, psychological, social, and lifestyle factors 57,58 and its heritability, which was found to range from 17% to 33%, for different dimensions. 59 In light of the aforementioned, the relationship of back and neck pain with HRQoL determined in our study can be considered practically significant and could serve as a hypothesis for future longitudinal studies on the causal relationship between these characteristics. A comparison of participants who reported back or neck pain never, rarely, sometimes, or often/almost always in average PCS and MCS scores showed that the presence of these conditions might considerably diminish overall HRQoL. Lower scores in PCS and MCS were associated with higher reported pain frequency in all analyses. Although most of the nearby groups did not differ significantly, all differences between nonadjacent and
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Fig 2. Differences in health-related quality according to back and neck pain frequency among males. A, Differences in PCS according to back pain frequency. B, Differences in PCS according to neck pain frequency. C, Differences in MCS according to back pain frequency. D, Differences in MCS according to neck pain frequency. *Category including participants who reported experiencing pain often or almost always. Bars denote mean values adjusted for age, BMI, and physical activity level, and whiskers denote their 95% CIs. opposite groups reached the level of practical importance suggested by Ware et al 51 (2-3 points on the PCS and 3 points on the MCS scale). Scores in overall physical and mental components of HRQoL were substantially lower in participants who reported back or neck pain often/almost always compared with those without back or neck pain. Average difference in PCS and MCS in all comparisons was approximately 10 points, which conforms to the value of 1 SD in US general population. 51 Therefore, a significant improvement in PCS and MCS with the effect size of approximately 1 SD might be expected as a nonclinical result of a successful treatment of severe or frequent chronic back/neck pain in Croatian adults. It seems that the magnitude of the difference obtained for PCS is rather constant across different studies. Crude difference in PCS scores was found to be − 7.5 points in adults (low back pain vs no back pain) 21 and − 11.2 points in elderly women (experiencing back pain daily vs infrequently). 27 In a study conducted on a general population, Rezai et al 18 found a mean difference of − 13.86 PCS points between severe neck pain and no neck pain groups. Findings for the association between back/neck pain and MCS were not so consistent in previous studies. Similar as in the current study, Rezai et al 18
found a mean difference in MCS of − 10.84 points between severe neck pain and no neck pain groups. In contrast, study by Zhu et al 27 showed a much smaller difference (− 2.00 points), and Hasanefendioglu et al 21 unexpectedly found lower MCS scores in the group without pain. Therefore, based on the current body of evidence, it would not be justified to draw a general conclusion about the relationship between back/neck pain and MCS.
Relationship of Back and Neck Pain With Life Satisfaction The life satisfaction was poorly or nonsignificantly correlated with back and neck pain in both sexes. However, low correlations determined between back and neck pain and life satisfaction should be interpreted by taking into account the high heritability of life satisfaction (38%) 48 and the fact that it is influenced by dozens of other factors. 60,61 Taking that into account, correlations of single variables such as back and neck pain with life satisfaction ranging from − 0.13 to − 0.17 are far from negligible. Although, in the current study, most of the correlations with life satisfaction did not even reach the level of statistical significance, it is possible that this was a consequence of
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applied Bonferroni adjustment. Namely, the adjustment of P values raises the probability of the type II error, especially in cases when correlations are low and number of comparisons is high. 62
Limitations and Strengths The interpretation of this study is subject to some limitations. First, the cross-sectional observational design as opposed to a longitudinal design does not allow for the examination of the causal relationship of back and neck pain with HRQoL. Second, we did not rely on a medical examination to diagnose back or neck pain but on the subjects' remembrance of the occurrences from a prior period, which may have resulted in recall bias. 63 The reliability of the self-report methods used in our study is far from perfect. A substantial amount of random measurement error might have affected our results by lowering true correlations between variables. Third, we assessed only frequency of pain and not its severity. Previous studies indicated that the crude relationship between pain severity (grade of pain intensity and associated disability) and HRQoL is negative. 18,20 However, the same was not true after adjustment for different confounding variables. 17,18 Because our study did not provide any new information on this issue, impact of back/neck pain severity on quality of life in Croatian population remains to be investigated in future studies. Fourth, a frequency of pain in various regions of the spine was not assessed. Future longitudinal studies should be conducted to elucidate separate influence of pain in different regions of the spine on HRQoL. Fifth, because of data availability, we did not control for other potential confounders, such as depression, comorbid conditions, and medication for pain. It is possible that the inclusion of more covariates in our analyses would reduce effect sizes, but this should be confirmed in future research. Sixth, relatively low response rate might have caused a certain bias, particularly in our prevalence estimates. It is possible that people without severe or frequent pain were more likely to agree to participate in the study. Finally, we used Spearman correlation to assess the relationships between variables. Using the nonparametric statistic can raise the probability of type II error. However, this might have biased only our conclusions about the relationship between back/neck pain and life satisfaction because all other correlations were significant, that is, obviously not affected by type II error. This study has several strengths. Standardized and validated questionnaires—SF-36 and SWLS—were used to assess HRQoL and life satisfaction. This study used the 8 dimensions of the SF-36 questionnaire in addition to the 2 summary scores, PCS and MCS. Based on previous research, use of the summary scores has a distinct advantage in evaluating HRQoL over other instruments, which exclude summary scores. 64 In addition, a large
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stratified random sample adds to the value of the study. The representative sample allowed us to generalize our results to the population of Croatian inhabitants 15 years or older.
CONCLUSION The results of this study showed that the prevalence of back and neck pain in Croatia is relatively high and that both conditions are strongly negatively related to HRQoL. Further improvements in the health care system and evidence-based public health interventions might be potential remedies to reduce the high prevalence rates. Furthermore, administrative bodies in primary care should initiate systematic monitoring of back and neck pain and related factors, as keeping a watchful eye on disorders affecting a population might help develop appropriate and effective prevention strategies.
Practical Applications • This is the first Croatian population-based study to examine the relationship of back and neck pain with HRQoL and life satisfaction. • Prevalence rates of back and neck pain in Croatian population were high for both men and women. • Back and neck pain showed moderate association with HRQoL and low association with life satisfaction in both females and males. • An increase in the reported pain frequency coincided with a practically significant decrease in the HRQoL. • Practitioners should expect significantly diminished self-perceived quality of life in patients with back and neck pain.
FUNDING SOURCES AND POTENTIAL CONFLICTS OF INTEREST No funding sources or conflicts of interest were reported for this study.
REFERENCES 1. WHO Scientific Group on the Burden of Musculoskeletal Conditions at the Start of the New Millennium. The burden of musculoskeletal conditions at the start of the new millennium. Geneva: World Health Organization; 2003. 2. Fejer R, Kyvik KO, Hartvigsen J. The prevalence of neck pain in the world population: a systematic critical review of the literature. Eur Spine J 2006;15:834-48. 3. Jones GT, Macfarlane GJ. Epidemiology of low back pain in children and adolescents. Arch Dis Child 2005;90:312-6.
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4. Maetzel A, Li L. The economic burden of low back pain: a review of studies published between 1996 and 2001. Best Pract Res Clin Rheumatol 2002;16:23-30. 5. Parthan A, Evans CJ, Le K. Chronic low back pain: epidemiology, economic burden and patient-reported outcomes in the USA. Expert Rev Pharmacoecon Outcomes Res 2006;6:359-69. 6. Martin BI, Deyo RA, Mirza SK, et al. Expenditures and health status among adults with back and neck problems. J Am Med Assoc 2008;299:656-64. 7. Fejer R, Hartvigsen J. Neck pain and disability due to neck pain: what is the relation? Eur Spine J 2008;17:80-8. 8. Niemeläinen R, Videman T, Battié MC. Prevalence and characteristics of upper or mid-back pain in Finnish men. Spine 2006;31:1846-9. 9. Côté P, Kristman V, Vidmar M, et al. The prevalence and incidence of work absenteeism involving neck pain. A cohort of Ontario lost-time claimants. J Manipulative Physiol Ther 2009;32:S219-26. 10. United States Department of Labor. Lost-worktime injuries and illnesses: characteristics and resulting time away from work, 2000. Washington, DC: Bureau of Labor Statistics; 2002. 11. Trinkoff AM, Lipscomb JA, Geiger-Brown J, Brady B. Musculoskeletal problems of the neck, shoulder, and back and functional consequences in nurses. Am J Ind Med 2002;41: 170-8. 12. Linton SJ, Hellsing AL, Halldén K. A population-based study of spinal pain among 35-45-year-old individuals. Prevalence, sick leave, and health care use. Spine 1998;23:1457-63. 13. Leboeuf-Yde C, Nielsen J, Kyvik KO, Fejer R, Hartvigsen J. Pain in the lumbar, thoracic or cervical regions: do age and gender matter? A population-based study of 34,902 Danish twins 20-71 years of age. BMC Musculoskelet Disord 2009;10. doi:10.1186/1471-2474-10-39. 14. Schneider S, Randoll D, Buchner M. Why do women have back pain more than men? A representative prevalence study in the Federal Republic of Germany. Clin J Pain 2006;22: 738-47. 15. Ono R, Higashi T, Takahashi O, et al. Sex differences in the change in health-related quality of life associated with low back pain. Qual Life Res 2012;21:1705-11. 16. Hoy D, Bain C, Williams G, et al. A systematic review of the global prevalence of low back pain. Arthritis Rheum 2012;64: 2028-37. 17. Côté P, Cassidy JD, Carroll L. The factors associated with neck pain and its related disability in the Saskatchewan population. Spine 2000;25:1109-17. 18. Rezai M, Côté P, Cassidy JD, Carroll L. The association between prevalent neck pain and health-related quality of life: a cross-sectional analysis. Eur Spine J 2009;18:371-81. 19. Suka M, Yoshida K. Low back pain deprives the Japanese adult population of their quality of life: a questionnaire survey at five healthcare facilities in Japan. Environ Health Prevent Med 2008;13:109-15. 20. Unsal A, Tozun M, Ayranci U. Prevalence of low back pain among a group of Turkish men and its effect on quality of life. Pak J Med Sci 2010;26:930-4. 21. Hasanefendioglu EZ, Sezgin M, Sungur MA, Cimen OB, Incel NA, Sahin G. Health-related quality of life in patients with Chronic low back pain: effects of pain, clinical and functional status on quality of life. Turk Fiz Tip Rehabil Derg 2012;58:93-8. 22. Horng YS, Hwang YH, Wu HC, et al. Predicting healthrelated quality of life in patients with low back pain. Spine 2005;30:551-5.
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23. Karjalainen K, Malmivaara A, Mutanen P, Pohjolainen T, Roine R, Hurri H. Outcome determinants of subacute low back pain. Spine 2003;28:2634-40. 24. Klemenc-Ketiš Z. Predictors of health-related quality of life and disability in patients with chronic non-specific low back pain. Zdr Vestn 2011;80:379-85. 25. Tavafian SS, Eftekhar H, Mohammad K, et al. Quality of life in women with different intensity of low back pain. Iran J Public Health 2005;34:36-9. 26. Balague F, Ferrer M, Rajmil L, Acuna AP, Pellise F, Cedraschi C. Assessing the association between low back pain, quality of life, and life events as reported by schoolchildren in a population-based study. Eur J Pediatr 2012;171: 507-14. 27. Zhu K, Devine A, Dick IM, Prince RL. Association of back pain frequency with mortality, coronary heart events, mobility, and quality of life in elderly women. Spine 2007; 32:2012-8. 28. Rantala MAI, Ahlberg J, Suvinen TI, et al. Temporomandibular joint related painless symptoms, orofacial pain, neck pain, headache, and psychosocial factors among non-patients. Acta Odontol Scand 2003;61:217-22. 29. Stålnacke BM. Relationship between symptoms and psychological factors five years after whiplash injury. J Rehabil Med 2009;41:353-9. 30. Peolsson M, Gerdle B. Coping in patients with chronic whiplash-associated disorders: a descriptive study. J Rehabil Med 2004;36:28-35. 31. Braš M, Milunović V, Boban M, et al. Quality of life in Croatian Homeland war (1991-1995) veterans who suffer from post-traumatic stress disorder and chronic pain. Health Qual Life Outcomes 2011;9. doi:10.1186/1477-7525-9-56. 32. Jajić Z, Rajnpreht I, Kovačić N, et al. Which clinical variables have the most significant correlation with quality of life evaluated by SF-36 survey in Croatian cohort of patient with ankylosing spondylitis and psoriatic arthritis. Rheumatol Int 2012;32:3471-9. 33. Paušić J, Pedišić Ž, Dizdar D. Reliability of a photographic method for assessing standing posture of elementary school students. J Manipulative Physiol Ther 2010;33:425-31. 34. Saad KR, Colombo AS, Amado João SM. Reliability and validity of the photogrammetry for scoliosis evaluation: a cross-sectional prospective study. J Manipulative Physiol Ther 2009;32:423-30. 35. Jurakić D, Pedišić Ž, Andrijašević M. Physical activity of Croatian population: cross-sectional study using International Physical Activity Questionnaire. Croat Med J 2009;50: 165-73. 36. Cohen J. A power primer. Psychol Bull 1992;112:155-9. 37. Ware JE, Sherbourne CD. The MOS 36-item short-form health survey (SF-36). I. Conceptual framework and item selection. Med Care 1992;30:473-83. 38. Ware JE. SF-36 Health Survey update. Spine 2000;25:3130-9. 39. Maslić Seršić D, Vuletić G. Psychometric evaluation and establishing norms of Croatian SF-36 Health Survey: framework for subjective health research. Croat Med J 2006;47:95-102. 40. Diener E, Emmons RA, Larsen RJ, Griffin S. The Satisfaction With Life Scale. J Pers Assess 1985;49:71-5. 41. Pavot W, Diener E. Review of the Satisfaction With Life Scale. Psychol Assessment 1993;5:164-72. 42. Vassar M. A note on the score reliability for the Satisfaction With Life Scale: an RG study. Soc Indic Res 2008;86:47-57. 43. Jurakić D, Pedišić Ž, Greblo Z. Physical activity in different domains and health-related quality of life: a population-based study. Qual Life Res 2010;19:1303-9.
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44. Fontaine KR, Barofsky I. Obesity and health-related quality of life. Obes Rev 2001;2:173-82. 45. Fryback DG, Dunham NC, Palta M, et al. US norms for six generic health-related quality-of-life indexes from the national health measurement study. Med Care 2007;45: 1162-70. 46. Ball K, Crawford D, Kenardy J. Longitudinal relationships among overweight, life satisfaction, and aspirations in young women. Obes Res 2004;12:1019-30. 47. Daig I, Herschbach P, Lehmann A, Knoll N, Decker O. Gender and age differences in domain-specific life satisfaction and the impact of depressive and anxiety symptoms: a general population survey from Germany. Qual Life Res 2009;18: 669-78. 48. Stubbe JH, Posthuma D, Boomsma DI, De Geus EJC. Heritability of life satisfaction in adults: a twin-family study. Psychol Med 2005;35:1581-8. 49. Craig CL, Marshall AL, Sjöström M, et al. International physical activity questionnaire: 12-country reliability and validity. Med Sci Sports Exerc 2003;35:1381-95. 50. Pedišić Ž, Jurakić D, Rakovac M, Hodak D, Dizdar D. Reliability of the Croatian long version of the international physical activity questionnaire. Kinesiology 2011;43: 185-91. 51. Ware JE, Snow KK, Kosinski M, Gandek B. SF-36 health survey: manual and interpretation guide. Lincoln, RI: QualityMetric Incorporated; 1993. 52. International Physical Activity Questionnaire (IPAQ). IPAQ Scoring Protocol. 2005. Available from: http://www.ipaq.ki. se/scoring.html. 53. Hoy DG, Protani M, De R, Buchbinder R. The epidemiology of neck pain. Best Pract Res Clin Rheumatol 2010; 24:783-92.
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54. Chiu TW, Leung SL, Lam KW. Neck pain in Hong Kong: a telephone survey on consequences and health service utilisation. Hong Kong Med J 2012;18(Suppl 3):13-5. 55. Walker J, Sofaer B, Holloway I. The experience of chronic back pain: accounts of loss in those seeking help from pain clinics. Eur J Pain 2006;10:199-207. 56. Leboeuf-Yde C, Fejer R, Nielsen J, Kyvik KO, Hartvigsen J. Consequences of spinal pain: do age and gender matter? A Danish cross-sectional population-based. BMC Musculoskelet Disord 2011;12. doi:10.1186/1471-2474-12-39. 57. Shields M, Shooshtari S. Determinants of self-perceived health. Health Rep 2001;13:35-52. 58. Rakovac M, Pedisic Z, Pranic S, Greblo Z, Hodak D. Sociodemographic and lifestyle correlates of health-related quality of life in Croatian university students. Appl Res Qual Life 2012. doi:10.1007/s11482-012-9203-9. 59. Romeis JC, Heath AC, Xian H, et al. Heritability of SF-36 among middle-age, middle-class, male-male twins. Med Care 2005;43:1147-54. 60. Fernández-Ballesteros R, Zamarrón MD, Ruíz MA. The contribution of socio-demographic and psychosocial factors to life satisfaction. Ageing Soc 2001;21:25-43. 61. Veenhoven R. Conditions of happiness. Dordrecht, Boston: Kluwer Academic; 1984. 62. Perneger TV. What's wrong with Bonferroni adjustments. Br Med J 1998;316:1236-8. 63. Linton SJ, Melin L. The accuracy of remembering chronic pain. Pain 1982;13:281-5. 64. Ware JE, Kosinski M, Bayliss MS, McHorney CA, Rogers WH, Raczek A. Comparison of methods for the scoring and statistical analysis of SF-36 health profile and summary measures: summary of results from the Medical Outcomes Study. Med Care 1995;33:AS264-79.
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ABSTRACT Objective: The purpose of this study was to determine the prevalence of back pain and neck pain and their relationship with the quality of life in the Croatian general population. Methods: This was a cross-sectional study using home-based face-to-face interviews of 1030 participants (51.6% females) 15 years or older. Back and neck pain frequencies were assessed using single items and quality of life using the Short Form Survey and Satisfaction with Life Scale. Analysis of covariance was conducted, where back pain or neck pain frequency was used as the categorical predictor; physical component summary or mental component summary, as the dependent variable; and age, body mass index, and physical activity level, as covariates. Results: The prevalence of back pain was 66.3% (95% confidence interval [CI], 62.3%-70.3%) and 62.9% (95% CI, 58.7%-67.2%) in females and males, respectively. The prevalence of neck pain was 58.0% (95% CI, 53.8%-62.2%) for females and 53.6 (95% CI, 49.2%-58.0%) for males. Differences between men and women were not significant (P N .05). Adjusted mean values for physical component summary and mental component summary were substantially lower in participants who reported back or neck pain often/almost always compared with those without pain. Differences ranged from 8.11 to 11.86 points (95% CI, 5.54-13.99) and from 9.61 to 10.99 points (95% CI, 7.3513.45) in females and males, respectively. Conclusions: The findings of this study showed that back and neck pain are highly prevalent and negatively related to quality of life in the Croatian general population. These data might raise the awareness of local government health authorities and lead to improvements in health care service for people with back and neck pain. (J Manipulative Physiol Ther 2013;36:267-275) Key Indexing Terms: Low Back Pain; Neck Pain; Chronic Pain; Quality of Life; Personal Satisfaction
ack and neck pain are growing public health problems. As many as 80% of adults experience back pain in their lifetime according to the World Health Organization. 1 The lifetime prevalence of neck pain for adults across different countries has been reported to range from 14.2% to 71.0%, with a 48.5% mean. 2 Evidence suggests that the prevalence of back and neck
B a
Researcher, Institute of Sport Science, Karl-Franzens-University of Graz, Graz, Austria. b Researcher/Lecturer, Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia. c Researcher/Lecturer, School of Medicine, University of Split, Split, Croatia. d Researcher/Lecturer, Faculty of Kinesiology, University of Zagreb, Zagreb, Croatia. Submit requests for reprints to: Zeljko Pedisic, PhD, Researcher/Lecturer, Horvacanski zavoj 15, HR-10000 Zagreb, Croatia (e-mail: [email protected]). Paper submitted October 31, 2012; in revised form March 9, 2013; accepted March 25, 2013. 0161-4754/$36.00 Copyright © 2013 by National University of Health Sciences. http://dx.doi.org/10.1016/j.jmpt.2013.05.012
pain is high even in children and adolescents. 2,3 Consequences of these conditions include economic burden, 4-6 disability, 7,8 occupational absenteeism, 9,10 and diminished work capacity. 6,11 Moreover, in studies examining pain in various regions of the spine, the overall prevalence rates are highest for low back pain followed by neck pain and mid back pain. 8,12,13 It has also been observed that women are more likely to experience back and neck pain. 2,12-16 Several studies have described the relationship of either back or neck pain with health-related quality of life (HRQoL). Most of them were conducted on different general adult populations 15,17-20 or patients with chronic back pain 21-25 and fewer on other populations such as schoolchildren 26 and elderly. 27 Despite of the valuable data from several studies, evidence on the relationship of back or neck pain with HRQoL in general population is still scarce, whereas methodological differences of the studies preclude drawing final conclusions. Furthermore, somewhat less attention has been given to the relationship between back or neck pain and life satisfaction. It has been studied in a working population 28 and in people with whiplashassociated disorders, 29,30 but, to the best of our knowledge, 267
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evidence collected from representative samples of the general population is still lacking. Little is known about the quality-of-life outcomes of back and neck pain in Croatia. Braš et al 31 investigated HRQoL in Croatian war veterans with posttraumatic stress disorder and low back pain, and Jajić et al 32 described the relationship between spinal pain and HRQoL in patients with ankylosing spondylitis and psoriatic arthritis. However, no recent studies have examined the prevalence of back/ neck pain or its relationship with the quality of life in the Croatian general population. Insight into these data might raise the awareness of local and regional government health authorities and lead to improvements in health care service for people with back and neck pain. Furthermore, it might motivate administrative bodies in primary care to initiate systematic monitoring of body posture and other factors, which may lead to the incidence of back and neck pain, especially nowadays when simple and affordable screening methods are available. 33,34 Besides, it might help patients, physicians, and allied health professionals better understand possible nonclinical benefits of back or neck pain treatment. Therefore, the purpose of this study was to determine the prevalence of back and neck pain and examine the relationship of these conditions with HRQoL and life satisfaction in the Croatian general population.
METHODS Subjects A cross-sectional study was conducted in November 2007 on a stratified random sample of 1076 Croatian inhabitants 15 years or older. Participants were interviewed face to face in their households. Unfortunately, no exact data on the response rate are available for the current study. Nevertheless, the survey company in charge of the sample selection and data collection indicated that the common response rate in similar household surveys that they regularly conduct in Croatia is approximately 35%. Sample stratification was performed by settlement size and geographical region using data from the Croatian 2001 census. At first, we randomly selected households. In each selected household, interviewers performed the random selection of 1 resident. The only eligibility criterion was that the selected resident is 15 years or older. A detailed description of the sample design can be found elsewhere. 35 Adult subjects gave written informed consent before being interviewed. Written consent was obtained from a parent or guardian after adolescent assent. To assure the anonymity of participants, upon completion of the interview, each questionnaire was sealed in an envelope with a barcode as the unique identifier. The identity of the participants was kept confidential and remained unknown to the researchers. The study protocol was approved by the Institutional Review Board at the Faculty of Kinesiology, University of Zagreb. All participants consented to participate in this study.
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Table 1. Sample characteristics x̄ ± s/% a Variable/category
Females
Males
Age (y) Size of settlement b b2000 2001-10 000 10 001-100 000 N100 000 Level of education Primary school Secondary school Undergraduate degree Graduate degree Postgraduate degree Household income per capita (€) BMI (kg/m2) b16.0 16.0-18.5 18.5-25 25-30 N 30
39.31 ± 14.97
38.99 ± 14.76
36.7 14.3 19.8 29.2
40.6 15.5 19.7 24.1
15.4 61.2 12.7 10.4 0.4 362.37 ± 253.72 24.00 ± 4.22 0.4 4.2 62.2 23.0 10.3
9.8 65.4 12.6 11.0 1.2 363.12 ± 216.38 26.23 ± 3.63 0.0 0.4 40.7 44.3 14.6
BMI, body mass index. a Mean ± SD (for quantitative variables)/percentages (for categories). b Number of inhabitants.
Because of incomplete data, 4.3% of the subjects were subsequently excluded from the study. The final sample consisted of 1030 subjects (51.6% females; mean age, 39.16 ± 14.86 years). The study sample is considered representative for the population of Croatian citizens 15 years or older. According to the Croatian 2011 census, there are somewhat more than 3.6 million Croatian inhabitants of the aforementioned age. General characteristics of the sample are presented in Table 1. Power analysis indicated that our sample size was large enough to detect significant differences at P b .05 using the analysis of covariance (ANCOVA) with an acceptable power of 0.77, if the true effect size in the population was at least small (F ≥ 0.10), according to Cohen. 36
Measures Frequency of back and neck pain was assessed using 2 separate questions (“How often have you recently experienced back pain?” and “How often have you recently experienced neck pain?”) with 5 possible answers: never, seldom, sometimes, often, and always. One-month testretest reliability of the questions was satisfactory (intraclass correlation coefficient, 0.53 for back pain and 0.49 for neck pain). Health-related quality of life was assessed using the Short-Form Health Survey (SF-36). 37 The questionnaire consists of 36 items that measure 8 dimensions of HRQoL: physical functioning, role physical, bodily pain, general health, vitality, social functioning, role emotional, and mental health. The aforementioned dimensions form 2 summary measures: physical component summary score
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(PCS) and mental component summary score (MCS). Physical component summary correlates most highly to the physical component scales (physical functioning, role physical, and bodily pain) and MCS to the mental component scales (social functioning, role emotional, and mental health). 38 General health, vitality, and social functioning share variance evenly with both summary measures. 38 Higher scores on SF-36 variables indicate a higher HRQoL. Previous studies have shown high reliability and validity of the Croatian version of SF-36 (internal consistency reliability range from 0.78 to 0.94). 39 Life satisfaction, which is viewed as people's perception of the difference between their reality and their aspirations and goals, was assessed using the Satisfaction with Life Scale (SWLS). 40 The questionnaire consists of five 5-point Likert scale items. The overall life satisfaction score was calculated as the arithmetic mean of all items. A higher score indicates higher life satisfaction and vice versa. Previous studies have shown high reliability (internal consistency reliability range from 0.79 to 0.89) and the single-factor structure of SWLS items. 40-42 In addition, we collected data on potential confounding variables: sex, age, body mass index (BMI), and physical activity level, as previous studies have shown their significant relation to HRQoL 43-45 and life satisfaction 46-48 in general population. Body mass index was calculated as weight/ height 2 (kilogram per square meter), according to the selfreported body weight and height. Total physical activity level was estimated in MET (metabolic equivalency of task)hours/week using the long version of the International Physical Activity Questionnaire (IPAQ), 49 which has shown satisfactory measurement properties in the Croatian general population. 50 Because of survey data availability, we did not consider including other potential confounding variables.
Pedisic, Pranic, and Jurakic Back and Neck Pain and Quality of Life
Table 2. Frequency of back and neck pain in Croatian general population RF, % (95% CI) Variable/category Back pain frequency Never Seldom Sometimes Often Almost always Neck pain frequency Never Rarely Sometimes Often Almost always
Females
Males
Pa
33.7 (29.7-37.7) 25.0 (21.4-28.7) 27.1 (23.3-30.9) 10.5 (7.9-13.2) 3.6 (2.0-5.2)
37.1 (32.8-41.3) 26.4 (22.5-30.3) 24.4 (20.6-28.2) 10.1 (7.4-12.7) 2.0 (0.8-3.3)
.257 .617 .319 .806 .131
42.0 (37.8-46.2) 23.9 (20.3-27.5) 22.4 (18.9-26.0) 9.0 (6.6-11.5) 2.6 (1.3-4.0)
46.4 (42.0-50.8) 23.6 (19.9-27.3) 21.0 (17.4-24.6) 7.5 (5.1-9.8) 1.6 (0.5-2.7)
.158 .902 .575 .358 .258
CI, confidence interval; RF, relative frequency. a P value for the difference between females and males.
between back and neck pain groups using series of ANCOVAs. Back or neck pain frequency was used as the categorical predictor; PCS or MCS, as the dependent variable; and age, BMI, and physical activity level, as covariates. Categories “often” and “almost always” according to back/ neck pain frequency were merged because of a low number of participants reporting pain almost always (1.6%-3.6%). To evaluate group-to-group differences, ANCOVA was followed by a post hoc test. Because sex has shown to be a strong determinant of HRQoL 45 and life satisfaction, 47 all analyses were conducted separately for females and males. Correlations and differences were considered statistically significant at a P b .05. Before significance testing, P values were adjusted for multiple significance tests using the Bonferroni correction.
RESULTS Data Analysis Data analyses were performed with IBM SPSS Statistics 19 (SPSS, Inc, an IBM Company, Chicago, IL). Although we used an automated data entry system using optical scanning, before analysis digital data were manually checked for errors. Data were screened for outliers and processed according to the SF-36 manual 51 and IPAQ scoring protocol. 52 Demographic and lifestyle variables are presented using mean ± SD. The prevalence rates of back and neck pain were expressed by percentages and the respective 95% confidence intervals (CIs). The prevalence rates in females and males were compared using the two-proportion z-test. Because most of the variables were not normally distributed, the relationship of back pain and neck pain with quality of life and life satisfaction was determined using partial Spearman rank correlation coefficients. Correlations were adjusted for age, BMI, and physical activity level. Normal distributions of PCS and MCS allowed us to explore differences in HRQoL
Prevalence of Back and Neck Pain The prevalence of back pain was 66.3% (95% CI, 62.3%70.3%) and 62.9% (95% CI, 58.7%-67.2%) in females and males, respectively (Table 2). The prevalence of neck pain was 58.0% (95% CI, 53.8%-62.2%) for females and 53.6 (95% CI, 49.2%-58.0%) for males. Around 80% of the participants who experienced back pain reported it as occurring rarely or sometimes. A similar percentage was determined for the participants experiencing neck pain rarely or sometimes. A frequent back or neck pain was much less prevalent. Differences between men and women in overall prevalence of back and neck pain were not significant (P = .26 for back pain and P = .16 for neck pain).
Correlation of Back and Neck Pain With HRQoL and Life Satisfaction All dimensions of HRQoL were significantly negatively correlated to back and neck pain in both females and males (P b .001) (Table 3). Notably, moderate correlations were
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Table 3. Relationship of back pain and neck pain with HRQoL and life satisfaction Females, r a (P) b
Males, r a (P) b
Quality of life variable
Back pain
Neck pain
Back pain
Neck pain
Physical functioning Role physical Bodily pain General health Vitality Social functioning Role emotional Mental health PCS MCS Life satisfaction
− 0.23 (b.001) − 0.32 (b.001) − 0.41 (b.001) − 0.33 (b.001) − 0.27 (b.001) − 0.37 (b.001) − 0.25 (b.001) − 0.25 (b.001) − 0.33 (b.001) − 0.29 (b.001) − 0.17 (.007)
− 0.26 (b.001) − 0.33 (b.001) − 0.47 (b.001) − 0.38 (b.001) − 0.23 (b.001) − 0.42 (b.001) − 0.28 (b.001) − 0.21 (b.001) − 0.42 (b.001) − 0.26 (b.001) − 0.13 (.212)
− 0.28 (b.001) − 0.24 (b.001) − 0.47 (b.001) − 0.37 (b.001) − 0.38 (b.001) − 0.43 (b.001) − 0.26 (b.001) − 0.32 (b.001) − 0.38 (b.001) − 0.34 (b.001) − 0.16 (.050)
− 0.27 (b .001) − 0.29 (b.001) − 0.43 (b.001) − 0.33 (b.001) − 0.38 (b.001) − 0.44 (b.001) − 0.24 (b.001) − 0.34 (b.001) − 0.35 (b.001) − 0.38 (b.001) − 0.15 (.077)
MCS, mental component summary score; PCS, physical component summary score. a Spearman rank correlation adjusted for age, BMI, and physical activity level. b Bonferroni-adjusted P value.
found for bodily pain, general health, social functioning, and PCS for both sexes. Moderate correlations were also found for role physical in females and for vitality, mental health, and MCS in males. Correlations with other HRQoL dimensions were low. Shared variance, calculated as squared correlation, between back and neck pain and HRQoL variables ranged from 4.4% to 22.1% and 5.8% to 22.1% in females and males, respectively. Life satisfaction was poorly correlated with back and neck pain in both females and males. The only significant correlation with life satisfaction was found for back pain in females.
Differences in HRQoL According to Back and Neck Pain Frequency All overall between-group differences in PCS and MCS using ANCOVAs were significant (P b .001) (Figs 1A-D and 2A-D). Among females, medium effect sizes according to Cohen 36 were found for differences between back pain groups in PCS (η 2 = 0.12) and MCS (η 2 = 0.08) and between neck pain groups in MCS (η 2 = 0.08). In the male sample, medium effect sizes were determined for differences between back pain groups in PCS (η 2 = 0.13) and between neck pain groups also in PCS (η 2 = 0.12). Comparisons of back and neck pain groups in MCS showed large effect sizes. Namely, both respective partial η 2 were 0.15. The analysis of differences between neck pain groups in PCS among females revealed the largest effect size among all comparisons (η 2 = 0.20). Post hoc analysis showed that most of the nearby groups had not differed significantly. Significant differences between adjusted mean values of nearby groups ranged from 2.35 to 6.35 (95% CI, 0.53-8.57) among females and from 3.05 to 5.47 (95% CI, 1.31-8.50) among males. Conversely, all comparisons of nonadjacent groups (never vs sometimes and rarely vs often/almost always), which are separated from each other by 1 category, and opposite groups (never vs often/almost always) resulted in significant differences (P b .001). Mean differences between nonadjacent groups
ranged from 4.08 to 9.51 (95% CI, 2.33-11.80) and 4.08 to 8.46 (95% CI, 2.28-11.01) among females and males, respectively. Differences between opposite groups were between 8.11 and 11.86 (95% CI, 5.54-13.99) in females and between 9.61 and 10.99 (95% CI, 7.35-13.45) in males.
DISCUSSION Prevalence of Back and Neck Pain Our study revealed a high prevalence of both back and neck pain in the Croatian adult population. When compared with other countries, Croatia would be placed among 10% with the highest prevalence of back pain, 16 and it would rank similarly high in regard to the prevalence of neck pain. 53 However, because of a methodological heterogeneity across previous studies, 16,53 these conclusions should be taken with caution. Inconsistent with other studies in which women generally reported the occurrence of back and neck pain more frequently than men, 2,12-16 we did not find significant differences between sexes. This might be due to real differences between Croatian and other survey populations but also due to discrepancy from other studies in the pain questionnaire used.
Relationship of Back and Neck Pain With HRQoL We found a significant relationship between back and neck pain and all HRQoL dimensions after adjustment for age, BMI, and physical activity level. Low to moderate correlations between back and neck pain and HRQoL were found in both females and males. The highest correlations were determined with bodily pain and social functioning scales. A large proportion of variance of back and neck pain shared with bodily pain (16.8%-22.1%) was expected due to the obvious contextual overlap in respective questionnaire items. In SF-36, bodily pain scale is assessed using following questions: “How much physical pain have you had during the past 4 weeks?” and “During the past 4
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Pedisic, Pranic, and Jurakic Back and Neck Pain and Quality of Life
Fig 1. Differences in health-related quality according to back and neck pain frequency among females. A, Differences in PCS according to back pain frequency. B, Differences in PCS according to neck pain frequency. C, Differences in MCS according to back pain frequency. D, Differences in MCS according to neck pain frequency. *Category including participants who reported experiencing pain often or almost always. Bars denote mean values adjusted for age, BMI, and physical activity level, and whiskers denote their 95% CIs. weeks, how much did pain interfere with your normal work?” It might be assumed that the participants experiencing back or neck pain were more likely to have worse scores on the bodily pain scale. Although it might also be that the relationship between these characteristics is bidirectional or even directed from bodily pain to back and neck pain frequency only, we believe that these are less possible explanations of the correlation. Furthermore, a high percentage of shared variance between back/neck pain and social functioning (13.7%-19.4%) was an expected finding, too. The social functioning items of SF-36 ask participant about time and extent in which physical health or emotional problems interfered with his/her social activities (like visiting friends, relatives, etc). Although we cannot conclude the causality of the relationship between back and neck and social functioning scales, our results suggest that people with back or neck pain are limited in attending social activities and events, which is congruent with previous findings. 54,55 Negative relationship of back/neck pain with physical functioning, role physical, and PCS is also in accordance with the results of previous studies. 20,21,25 It has been shown that back and neck pain reduce physical activity 56 and working
capacity 6,11 and cause disability 7,8 and occupational absenteeism. 9,10 All of the aforementioned consequences of back/neck pain are likely to be direct causes of diminished scores in physical dimensions of HRQoL. The magnitude of relationship between back and neck pain and HRQoL variables should be considered in the context of the complexity of HRQoL, that is, its dependence on a wide variety of health, psychological, social, and lifestyle factors 57,58 and its heritability, which was found to range from 17% to 33%, for different dimensions. 59 In light of the aforementioned, the relationship of back and neck pain with HRQoL determined in our study can be considered practically significant and could serve as a hypothesis for future longitudinal studies on the causal relationship between these characteristics. A comparison of participants who reported back or neck pain never, rarely, sometimes, or often/almost always in average PCS and MCS scores showed that the presence of these conditions might considerably diminish overall HRQoL. Lower scores in PCS and MCS were associated with higher reported pain frequency in all analyses. Although most of the nearby groups did not differ significantly, all differences between nonadjacent and
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Fig 2. Differences in health-related quality according to back and neck pain frequency among males. A, Differences in PCS according to back pain frequency. B, Differences in PCS according to neck pain frequency. C, Differences in MCS according to back pain frequency. D, Differences in MCS according to neck pain frequency. *Category including participants who reported experiencing pain often or almost always. Bars denote mean values adjusted for age, BMI, and physical activity level, and whiskers denote their 95% CIs. opposite groups reached the level of practical importance suggested by Ware et al 51 (2-3 points on the PCS and 3 points on the MCS scale). Scores in overall physical and mental components of HRQoL were substantially lower in participants who reported back or neck pain often/almost always compared with those without back or neck pain. Average difference in PCS and MCS in all comparisons was approximately 10 points, which conforms to the value of 1 SD in US general population. 51 Therefore, a significant improvement in PCS and MCS with the effect size of approximately 1 SD might be expected as a nonclinical result of a successful treatment of severe or frequent chronic back/neck pain in Croatian adults. It seems that the magnitude of the difference obtained for PCS is rather constant across different studies. Crude difference in PCS scores was found to be − 7.5 points in adults (low back pain vs no back pain) 21 and − 11.2 points in elderly women (experiencing back pain daily vs infrequently). 27 In a study conducted on a general population, Rezai et al 18 found a mean difference of − 13.86 PCS points between severe neck pain and no neck pain groups. Findings for the association between back/neck pain and MCS were not so consistent in previous studies. Similar as in the current study, Rezai et al 18
found a mean difference in MCS of − 10.84 points between severe neck pain and no neck pain groups. In contrast, study by Zhu et al 27 showed a much smaller difference (− 2.00 points), and Hasanefendioglu et al 21 unexpectedly found lower MCS scores in the group without pain. Therefore, based on the current body of evidence, it would not be justified to draw a general conclusion about the relationship between back/neck pain and MCS.
Relationship of Back and Neck Pain With Life Satisfaction The life satisfaction was poorly or nonsignificantly correlated with back and neck pain in both sexes. However, low correlations determined between back and neck pain and life satisfaction should be interpreted by taking into account the high heritability of life satisfaction (38%) 48 and the fact that it is influenced by dozens of other factors. 60,61 Taking that into account, correlations of single variables such as back and neck pain with life satisfaction ranging from − 0.13 to − 0.17 are far from negligible. Although, in the current study, most of the correlations with life satisfaction did not even reach the level of statistical significance, it is possible that this was a consequence of
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applied Bonferroni adjustment. Namely, the adjustment of P values raises the probability of the type II error, especially in cases when correlations are low and number of comparisons is high. 62
Limitations and Strengths The interpretation of this study is subject to some limitations. First, the cross-sectional observational design as opposed to a longitudinal design does not allow for the examination of the causal relationship of back and neck pain with HRQoL. Second, we did not rely on a medical examination to diagnose back or neck pain but on the subjects' remembrance of the occurrences from a prior period, which may have resulted in recall bias. 63 The reliability of the self-report methods used in our study is far from perfect. A substantial amount of random measurement error might have affected our results by lowering true correlations between variables. Third, we assessed only frequency of pain and not its severity. Previous studies indicated that the crude relationship between pain severity (grade of pain intensity and associated disability) and HRQoL is negative. 18,20 However, the same was not true after adjustment for different confounding variables. 17,18 Because our study did not provide any new information on this issue, impact of back/neck pain severity on quality of life in Croatian population remains to be investigated in future studies. Fourth, a frequency of pain in various regions of the spine was not assessed. Future longitudinal studies should be conducted to elucidate separate influence of pain in different regions of the spine on HRQoL. Fifth, because of data availability, we did not control for other potential confounders, such as depression, comorbid conditions, and medication for pain. It is possible that the inclusion of more covariates in our analyses would reduce effect sizes, but this should be confirmed in future research. Sixth, relatively low response rate might have caused a certain bias, particularly in our prevalence estimates. It is possible that people without severe or frequent pain were more likely to agree to participate in the study. Finally, we used Spearman correlation to assess the relationships between variables. Using the nonparametric statistic can raise the probability of type II error. However, this might have biased only our conclusions about the relationship between back/neck pain and life satisfaction because all other correlations were significant, that is, obviously not affected by type II error. This study has several strengths. Standardized and validated questionnaires—SF-36 and SWLS—were used to assess HRQoL and life satisfaction. This study used the 8 dimensions of the SF-36 questionnaire in addition to the 2 summary scores, PCS and MCS. Based on previous research, use of the summary scores has a distinct advantage in evaluating HRQoL over other instruments, which exclude summary scores. 64 In addition, a large
Pedisic, Pranic, and Jurakic Back and Neck Pain and Quality of Life
stratified random sample adds to the value of the study. The representative sample allowed us to generalize our results to the population of Croatian inhabitants 15 years or older.
CONCLUSION The results of this study showed that the prevalence of back and neck pain in Croatia is relatively high and that both conditions are strongly negatively related to HRQoL. Further improvements in the health care system and evidence-based public health interventions might be potential remedies to reduce the high prevalence rates. Furthermore, administrative bodies in primary care should initiate systematic monitoring of back and neck pain and related factors, as keeping a watchful eye on disorders affecting a population might help develop appropriate and effective prevention strategies.
Practical Applications • This is the first Croatian population-based study to examine the relationship of back and neck pain with HRQoL and life satisfaction. • Prevalence rates of back and neck pain in Croatian population were high for both men and women. • Back and neck pain showed moderate association with HRQoL and low association with life satisfaction in both females and males. • An increase in the reported pain frequency coincided with a practically significant decrease in the HRQoL. • Practitioners should expect significantly diminished self-perceived quality of life in patients with back and neck pain.
FUNDING SOURCES AND POTENTIAL CONFLICTS OF INTEREST No funding sources or conflicts of interest were reported for this study.
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