Scand J Rheumatol 2014;43:419–423
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Mental health indicators and quality of life among individuals with musculoskeletal chronic pain: a nationwide study in Iceland SV Björnsdóttir1, SH Jónsson2,3, UA Valdimarsdóttir4,5
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1 Department of Physical Therapy, Faculty of Medicine, University of Iceland, Reykjavík, 2Directorate of Health, Reykjavík, 3Department of Social Sciences, Faculty of Social and Human Sciences, University of Iceland, Reykjavík, 4Centre of Public Health Sciences, Faculty of Medicine, University of Iceland, Reykjavík, Iceland, and 5Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA
Objectives: Musculoskeletal chronic pain is a costly public health threat. The aim of our study was to investigate mental health indicators, including self-reported symptoms of depression, sleep disruption, stress, well-being, and quality of life (QoL), among men and women with musculoskeletal chronic pain in a general population. Method: This was a cross-sectional study; a postal questionnaire was mailed to a stratified random sample of 9807 eligible Icelanders retrieved from a national registry, of whom 5906 responded (response rate ¼ 60.2%). Chronic pain conditions included reports of current chronic back pain, chronic neck symptoms, and/or fibromyalgia. Gender-stratified associations of chronic pain conditions with mental health indicators were estimated with logistic regression analyses adjusting for age, income, body mass index (BMI), smoking, education, and residence. Results: We observed higher odds of low satisfaction with life [adjusted odds ratio (ORadj) women 2.0, 95% confidence interval (CI) 1.5–2.6; ORadj men 2.3, 95% CI 1.7–3.1], higher levels of perceived stress (ORadj women 1.7, 95% CI 1.3– 2.2; ORadj men ¼ 1.5, 95% CI 1.1–2.1), depressive symptoms (ORadj women 2.4, 95% CI 1.9–3.0; ORadj men 2.8, 95% CI 2.1–3.7), and sleep disruption (ORadj women 2.8, 95% CI 2.2–3.5; ORadj men 2.2, 95% CI 1.5–3.1), and diminished QoL (ORadj women 1.6, 95% CI 1.2–2.1; ORadj men 1.5, 95% CI 1.0–2.1) among individuals with chronic pain compared with those without the condition. Conclusions: Our data indicate that individuals with musculoskeletal chronic pain have increased risk of poor mental health and diminished QoL. Further studies are needed on treatment and preventative measures of a decline in mental health among individuals with chronic pain.
Diminished quality of life (QoL) has been observed among people with chronic pain conditions in populationbased (1) and clinical samples (2–4). Data from population-based studies are essential for a realistic picture of the mental health of individuals with chronic pain. Therefore, using a national representative sample, the aim was to investigate mental health indicators in terms of depressive symptoms, sleep disruption, stress, wellbeing, and QoL of men and women with self-reported chronic musculoskeletal pain.
Method In this cross-sectional study we used data from a general health survey conducted in Iceland in 2007 (5). In total, 5906 out of 9807 eligible individuals (identified from the National Registry) responded to a postal questionnaire Sigrún Vala Björnsdóttir, Department of Physical Therapy, Stapi v/Hringbraut, 101 Reykjavik, Iceland. E-mail: [email protected] Accepted 6 January 2014
(60.2%). The study was approved by the Icelandic bioethics committee. The random sample stratified by age and residence included proportionally more individuals of older age and from urban areas compared with the distribution in the population.
Questionnaires We used a single validated question (four-point scale) from the mail survey ‘The health and well-being of the Icelandic population 2007’ (5), which included 98 questions, to measure general mental health (6). We used the validated European Social Survey measure on happiness (7). To measure well-being we used the validated sevenquestion Short Warwick-Edinburgh Mental Well-being Scale (SWEMWBS) (8). Summary scores range between 7 and 35, with a higher score meaning better well-being. For this study, the total sample’s mean was calculated and the score representing one standard deviation (SD) under the mean was selected as the reference. The mean was 25.04 (SD ¼ 4.21), yielding < 20.83 as the reference for poor well-being. Cronbach’s α for the sample was 0.86.
© 2014 Informa Healthcare on license from Scandinavian Rheumatology Research Foundation DOI: 10.3109/03009742.2014.881549
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We also used the validated five-item Satisfaction With Life Scale (SWLS) (9). Summary scores are from 5 to 35, with 20 representing a neutral point. We used our SWEMWBS methodology, yielding a mean of 26.19 (SD ¼ 5.62) determining 20 as the reference. Cronbach’s α for the sample was 0.91. Level of stress was measured with the validated fouritem Perceived Stress Scale (PSS) (10). The scoring ranges between 0 and 16. We used our SWEMWBS methodology, yielding a mean of 4.24 (SD ¼ 2.89) and revealing 7 as the reference for stress. Cronbach’s α for the sample was 0.68. The five-item World Health Organization well-being index (WHO-5) has been used to measure depressive symptoms. A score < 13 should indicate further testing for depression (11); therefore, the standard cut-off score of < 13 was used. Cronbach’s α for the sample was 0.82. A four-item questionnaire on sleep disruption was designed for this study. The measure is on a five-point scale. A summary score was calculated and our SWEMWBS methodology used, yielding a mean of 10.0 (SD ¼ 3.07) and determining > 13 as the reference. Cronbach’s α for the sample was 0.73. The questionnaire was initially tested on university students and eight volunteers for cognitive interviewing. The wording of adaptations was checked.
SV Björnsdóttir et al
response rate by gender. Variables on mental health indicators were dichotomized. For comparison of variables of interest among people with C-CPD vs. controls, a logistic regression analysis was used to compute odds ratios (ORs) with 95% confidence intervals (CIs). With the same variables included, we further ran linear models, contrasting means of mental health indicators on a continuous scale between individuals with and without chronic pain. We observed similar results as in the logistic regression (data not shown). Backward selection was used to identify the best regression model to control for potential confounding factors in further analyses. The selected model included gender, age, monthly income, body mass index (BMI), smoking, and educational level. For weighting purposes, the final model also included the variable residence but the variable gender was excluded because of gender stratification. SPSS version 19 was used for the statistical analyses.
Results
Variables with missing values were completed with imputation, where imputation was likely to minimize systematic error due to answering styles (5). Potential confounding variables were categorized. Age was treated throughout the analyses in six categories as during sampling.
The data from the health survey contain responses from 2724 men and 3108 women (missing values on gender ¼ 74). Background characteristics of the study participants are presented in Table 1. In summary, our results indicate that the estimated prevalence of C-CPD is higher among women (24.7%) than men (15.2%), and increases with age (15.2% at 18–39 years, 27.7% at 60–79 years), decreased income [25.3% 200 000 Icelandic krona (IKR), 14.1% 370 000 IKR], less educational level (26.0% primary school, 13.6% university), and smoking (22.8% current or past smoker, 16.4% never smoked). Table 2 shows gender-stratified comparisons of selfassessed mental health, QoL, life satisfaction, stress, depressive symptoms, and sleep disruption in those reporting C-CPD vs. N-CPD in our population-based sample. Overall, higher odds of poor mental health and depressive symptoms were observed in individuals reporting C-CPD vs. N-CPD. In addition, higher odds of poor QoL, dissatisfaction with life, depressive symptoms, stress, and sleep disruption were observed. As fibromyalgia constitutes a distinct diagnostic entity from other chronic pain conditions, we repeated our main analyses without individuals reporting fibromyalgia. The results remained the same (data not shown) with the exception that, on excluding fibromyalgia, there was no difference in happiness between women reporting C-CPD and N-CPD [adjusted OR (ORadj ) 1.3, 95% CI 0.9–1.9].
Analytical strategy
Discussion
Weighted data analyses were applied to adjust the raw survey data to represent the population from which the sample was drawn. Population estimates are therefore based on weighted data to account for over-representation of older age groups in the sample and to adjust for uneven
The findings from our nationwide survey, using a randomly attained, stratified sample of nearly 5700 Icelanders, indicate that individuals with chronic musculoskeletal pain report deficient mental health. Both men and women with musculoskeletal chronic pain tend to be more
Chronic pain conditions The present survey included a question on chronic conditions, including items on chronic back pain, chronic neck symptoms, and fibromyalgia. The questions were stated individually, such as: Have you ever had fibromyalgia/chronic back pain/chronic symptoms in the neck? The response options were: yes now, yes but not now, no never. People reporting currently having any of these conditions met our criteria for current chronic pain disorder (C-CPD; n ¼ 1292). Those reported not having any of the conditions formed the reference population (non-chronic pain disorder, N-CPD; n ¼ 4464). Management of variables
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Table 1. Characteristics of Icelanders reporting current chronic pain in December 2007, a self-completed sample of adults.
Prevalence in November to December 2007 Gender Men Women Age 18–39 years 40–59 years 60–79 years Marital status Living alone Living with partner Number of children No children One child 2 children Residence Capital area Country side Monthly income 200 000 IKR 201 000–369 000 IKR 370 000 IKR Social status Employed Unemployed Educational level Primary school (9–10 years) College/high school University Smoking Never smoked Current or past smoker Body mass index Current chronic pain No chronic pain
Chronic pain disorder
Chronic back pain
Chronic neck symptoms
Fibromyalgia
1292/5756 (19.9)
1022/5678 (16.2)
171/5667 (2.6)
369/5555 (5.3)
473/2673 (15.2) 807/3023 (24.7)
404/2636 (13.6) 608/2984 (19.0)
62/2632 (1.8) 108/2979 (3.4)
59/2594 (1.6) 306/2906 (9.2)
269/1669 (15.2) 438/1997 (21.2) 571/2031 (27.7)
236/1657 (13.6) 330/1977 (16.4) 446/1987 (21.9)
21/1661 (1.2) 73/1969 (3.6) 75/1982 (3.7)
51/1658 (2.4) 150/1950 (7.0) 164/1893 (8.7)
357/1482 (19.5) 921/4220 (19.9)
290/1459 (16.4) 722/4167 (16.1)
51/1455 (2.7) 119/4162 (2.6)
99/1431 (5.2) 265/4078 (5.3)
161/956 (14.4) 127/604 (18.9) 988/4125 (22.2)
140/945 (13.1) 109/602 (16.7) 761/4062 (17.4)
12/945 (1.0) 11/598 (1.5) 146/4058 (3.4)
32/938 (2.5) 25/593 (3.5) 305/3958 (6.9)
595/2735 (19.0) 671/2921 (21.3)
471/2702 (15.6) 534/2878 (17.4)
83/2701 (2.6) 80/2869 (2.5)
166/2652 (5.0) 193/2808 (6.0)
679/2403 (25.3) 334/1708 (18.3) 197/1309 (14.1)
534/2364 (20.9) 272/1692 (15.2) 159/1296 (11.3)
99/2352 (3.6) 37/1690 (2.2) 23/1298 (1.7)
216/2283 (7.6) 74/1664 (4.1) 45/1293 (3.1)
754/4078 (17.2) 481/1476 (30.2)
588/1033 (14.0) 393/1448 (25.1)
84/4038 (1.9) 76/1436 (5.1)
189/3988 (3.9) 159/1385 (10.6)
625/2260 (26.0) 270/1391 (17.2) 177/1251 (13.6)
502/224 (21.6) 220/1377 (14.5) 140/1241 (10.9)
79/2218 (3.4) 33/1378 (2.0) 20/1239 (1.6)
177/2153 (7.1) 71/1361 (4.1) 52/1230 (3.8)
426/2273 (16.4) 798/3166 (22.8)
327/2242 (13.2) 642/3127 (18.8)
60/2247 (2.4) 101/3116 (2.7)
122/2214 (4.1) 226/3049 (6.3)
27.8 5.5 26.4 4.7
27.6 5.4 26.5 4.8
27.9 6.4 26.6 4.8
28.9 5.7 26.5 4.8
IKR, Icelandic krona (local currency). Values given as n/N (%) or weighted mean SD, where n/N is the number/number in sample (population estimate), and population estimate is calculated through weight including gender, age, and residential area.
affected by perceived stress, depressive symptoms, sleep disruption, and life dissatisfaction than those without the condition. Our results support the hypothesis of a negative impact of chronic pain on mental health indicators, with our population-based data providing a realistic picture of mental health problems of individuals with chronic pain, in a naturalistic setting. This is indeed the first Icelandic study to provide in-depth information on the mental health status of people with chronic pain. Our observations that people with chronic pain conditions in a general population are subject to diminished QoL and well-being are in accordance with clinical studies on various chronic pain conditions (2–4, 12). Furthermore, in accordance with our results, Demyttenaere et al concluded that people in general populations reporting chronic pain problems also experience depression (and anxiety), independent of cultural or demographic origins (13). Notably, our findings indicate that men and women with chronic pain present with equally elevated ORs of mental health problems. Strengths of this study lie in the reasonable sample size of a representative sample from an underlying
population and the acceptable response rate. Initial studies further indicate that respondents were fairly similar to non-respondents in terms of age and population characteristics (5). The cross-sectional study design is an important limitation in this study, prohibiting inferences on the direction of associations observed. Information bias further constitutes a threat to the validity of data in studies relying on selfreports; in this study, individuals may, for example, either over- or under-report the measured mental health indicators. However, to distort the reported associations based on self-reports, individuals with chronic pain would need to have responded differently to the questionnaire from those not experiencing the condition. We have no indication for or against this claim, but caution is needed when interpreting the data. Finally, the diagnosis of chronic pain has been reported to lack validity (14) and the self-reported data of this study neither reflect an established diagnosis nor offer information on all conditions related to chronic widespread pain. These limitations should be
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Table 2. Self-assessed mental health indicators and quality of life (QoL) among adult individuals with and without current chronic pain. Women
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n/N (%) Poor mental health, in general No chronic pain Chronic pain Feeling unhappy (from the European Social Survey) No chronic pain Chronic pain Poor well-being and diminished QoL measured with the SWEMWBS No chronic pain Chronic pain Dissatisfaction with life measured with the SWLS No chronic pain Chronic pain Stress measured with the PSS No chronic pain Chronic pain Potential depression measured on the WHO-5 well-being index No chronic pain Chronic pain Sleeping disturbances measured with a self-designed questionnaire No chronic pain Chronic pain
OR
Men
adj
95% CI
n/N (%)
ORadj
95% CI
304/2205 (13.8) 257/800 (32.1)
1 2.4
1.9–3.0
353/2172 (16.3) 136/462 (29.4)
1 1.7
1.3–2.3
166/2136 (7.8) 108/778 (13.9)
1 1.6
1.2–2.2
191/2151 (8.9) 80/460 (17.4)
1 1.7
1.2–2.4
242/2093 (11.6) 135/734 (18.4)
1 1.6
1.2–2.1
253/2083 (12.1) 85/446 (19.1)
1 1.5
1.0–2.1
230/2120 (10.8) 177/766 (23.1)
1 2.0
1.5–2.6
281/2136 (13.2) 127/458 (27.7)
1 2.3
1.7–3.1
307/2110 (14.5) 171/765 (22.4)
1 1.7
1.3–2.2
243/2111 (11.5) 81/452 (17.9)
1 1.5
1.1–2.1
352/2119 (16.6) 256/769 (33.3)
1 2.4
1.9–3.0
308/2129 (14.5) 138/452 (30.5)
1 2.8
2.1–3.7
277/2067 (13.4) 237/762 (31.1)
1 2.8
2.2–3.5
180/2095 (8.6) 89/447 (19.9)
1 2.2
1.5–3.1
adj
OR , Odds ratio adjusted for age, monthly income, body mass index, smoking, educational level, and residential area; CI, confidence interval; SWEMWBS, Short Warwick–Edinburgh Mental Well-Being Scale; SWLS, Satisfaction With Life Scale; PSS, Perceived Stress Scale.
kept in mind when interpreting the results. As the Icelandic population is fairly homogeneous in terms of ethnicity and culture, caution should be exercised when generalizing findings to other populations. In our previous work we reported that individuals with chronic pain report various physical concerns and functional limitations (15) and our current study adds evidence that several mental health indicators are also applicable in this population. Together these studies provide a comprehensive picture of the global health symptomatology affecting individuals with chronic pain in the larger general population. We conclude that Icelanders in the general population who report chronic pain are subject to increased risk of declining mental health and diminishing QoL. Future research needs to focus on treatment and preventative measures of a decline in mental health among individuals with chronic pain.
Acknowledgements This project was funded by grants from the Association of Icelandic Physical Therapists and from the Lifelong Learning Centre in Southern Iceland. We thank the Public Health Institute for providing access to the data from the health survey.
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References 1. Sjøgren P, Ekholm O, Peuckmann V, Grønbæk M. Epidemiology of chronic pain in Denmark: an update. Eur J Pain 2009;13:287–92. 2. Becker N, Bondegaard Thomsen A, Olsen AK, Sjøgren P, Bech P, Eriksen J. Pain epidemiology and health related quality of life in chronic non-malignant pain patients referred to a Danish multidisciplinary pain center. Pain 1997;73:393–400. 3. Lin R-F, Chang J-J, Lu Y-M, Huang M-H, Lue Y-J. Correlations between quality of life and psychological factors in patients with chronic neck pain. Kaohsiung J Med Sci 2010;26:13–20. 4. Laursen BS, Bajaj P, Olesen AS, Delmar C, Arendt-Nielsen L. Health related quality of life and quantitative pain measurement in females with chronic non-malignant pain. Eur J Pain 2005; 9:267–75. 5. Jónsson SH, Guðlaugsson JÓ, Gylfason HF, Guðmundsdóttir DG. Health and well-being of Icelanders 2007: project report. Reykjavik, Iceland: Public Health Institute, 2011. 6. Hays R, Bjorner J, Revicki D, Spritzer K, Cella D. Development of physical and mental health summary scores from the patient-reported outcomes measurement information system (PROMIS) global items. Qual Life Res 2009;18:873–80. 7. Abdel-Khalek AM. Measuring happiness with a single-item scale. Soc Behav Pers 2006;34:139. 8. Tennant R, Hiller L, Fishwick R, Platt S, Joseph S, Weich S, et al. The Warwick-Edinburgh Mental Well-being Scale (WEMWBS): development and UK validation. Health Qual Life Outcomes 2007;5:63. 9. Diener E, Emmons RA, Larsen RJ, Griffin S. The Satisfaction With Life Scale. J Pers Assess 1985;49:71–5.
Mental health indicators to chronic pain
13. Demyttenaere K, Bruffaerts R, Lee S, Posada-Villa J, Kovess V, Angermeyer MC, et al. Mental disorders among persons with chronic back or neck pain: results from the World Mental Health Surveys. Pain 2007;129:332–42. 14. Lindell L, Bergman S, Petersson IF, Jacobsson LTH, Herrström P. Prevalence of fibromyalgia and chronic widespread pain. Scand J Prim Health Care 2000;18:149–53. 15. Björnsdóttir S, Jónsson S, Valdimarsdóttir U. Functional limitations and physical symptoms of individuals with chronic pain. Scand J Rheumatol 2013;42:59–70.
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10. Leung D, Lam T-H, Chan S. Three versions of Perceived Stress Scale: validation in a sample of Chinese cardiac patients who smoke. BMC Public Health 2010; 10:513. 11. Mastering depression in primary care. Frederiksborg: World Health Organization Regional Office for Europe, Psychiatric Research Unit, 1998. 12. Lamé IE, Peters ML, Vlaeyen JWS, Kleef Mv, Patijn J. Quality of life in chronic pain is more associated with beliefs about pain, than with pain intensity. Eur J Pain 2005;9:15–24.
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Mental health indicators and quality of life among individuals with musculoskeletal chronic pain: a nationwide study in Iceland SV Björnsdóttir1, SH Jónsson2,3, UA Valdimarsdóttir4,5
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1 Department of Physical Therapy, Faculty of Medicine, University of Iceland, Reykjavík, 2Directorate of Health, Reykjavík, 3Department of Social Sciences, Faculty of Social and Human Sciences, University of Iceland, Reykjavík, 4Centre of Public Health Sciences, Faculty of Medicine, University of Iceland, Reykjavík, Iceland, and 5Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA
Objectives: Musculoskeletal chronic pain is a costly public health threat. The aim of our study was to investigate mental health indicators, including self-reported symptoms of depression, sleep disruption, stress, well-being, and quality of life (QoL), among men and women with musculoskeletal chronic pain in a general population. Method: This was a cross-sectional study; a postal questionnaire was mailed to a stratified random sample of 9807 eligible Icelanders retrieved from a national registry, of whom 5906 responded (response rate ¼ 60.2%). Chronic pain conditions included reports of current chronic back pain, chronic neck symptoms, and/or fibromyalgia. Gender-stratified associations of chronic pain conditions with mental health indicators were estimated with logistic regression analyses adjusting for age, income, body mass index (BMI), smoking, education, and residence. Results: We observed higher odds of low satisfaction with life [adjusted odds ratio (ORadj) women 2.0, 95% confidence interval (CI) 1.5–2.6; ORadj men 2.3, 95% CI 1.7–3.1], higher levels of perceived stress (ORadj women 1.7, 95% CI 1.3– 2.2; ORadj men ¼ 1.5, 95% CI 1.1–2.1), depressive symptoms (ORadj women 2.4, 95% CI 1.9–3.0; ORadj men 2.8, 95% CI 2.1–3.7), and sleep disruption (ORadj women 2.8, 95% CI 2.2–3.5; ORadj men 2.2, 95% CI 1.5–3.1), and diminished QoL (ORadj women 1.6, 95% CI 1.2–2.1; ORadj men 1.5, 95% CI 1.0–2.1) among individuals with chronic pain compared with those without the condition. Conclusions: Our data indicate that individuals with musculoskeletal chronic pain have increased risk of poor mental health and diminished QoL. Further studies are needed on treatment and preventative measures of a decline in mental health among individuals with chronic pain.
Diminished quality of life (QoL) has been observed among people with chronic pain conditions in populationbased (1) and clinical samples (2–4). Data from population-based studies are essential for a realistic picture of the mental health of individuals with chronic pain. Therefore, using a national representative sample, the aim was to investigate mental health indicators in terms of depressive symptoms, sleep disruption, stress, wellbeing, and QoL of men and women with self-reported chronic musculoskeletal pain.
Method In this cross-sectional study we used data from a general health survey conducted in Iceland in 2007 (5). In total, 5906 out of 9807 eligible individuals (identified from the National Registry) responded to a postal questionnaire Sigrún Vala Björnsdóttir, Department of Physical Therapy, Stapi v/Hringbraut, 101 Reykjavik, Iceland. E-mail: [email protected] Accepted 6 January 2014
(60.2%). The study was approved by the Icelandic bioethics committee. The random sample stratified by age and residence included proportionally more individuals of older age and from urban areas compared with the distribution in the population.
Questionnaires We used a single validated question (four-point scale) from the mail survey ‘The health and well-being of the Icelandic population 2007’ (5), which included 98 questions, to measure general mental health (6). We used the validated European Social Survey measure on happiness (7). To measure well-being we used the validated sevenquestion Short Warwick-Edinburgh Mental Well-being Scale (SWEMWBS) (8). Summary scores range between 7 and 35, with a higher score meaning better well-being. For this study, the total sample’s mean was calculated and the score representing one standard deviation (SD) under the mean was selected as the reference. The mean was 25.04 (SD ¼ 4.21), yielding < 20.83 as the reference for poor well-being. Cronbach’s α for the sample was 0.86.
© 2014 Informa Healthcare on license from Scandinavian Rheumatology Research Foundation DOI: 10.3109/03009742.2014.881549
www.scandjrheumatol.dk
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We also used the validated five-item Satisfaction With Life Scale (SWLS) (9). Summary scores are from 5 to 35, with 20 representing a neutral point. We used our SWEMWBS methodology, yielding a mean of 26.19 (SD ¼ 5.62) determining 20 as the reference. Cronbach’s α for the sample was 0.91. Level of stress was measured with the validated fouritem Perceived Stress Scale (PSS) (10). The scoring ranges between 0 and 16. We used our SWEMWBS methodology, yielding a mean of 4.24 (SD ¼ 2.89) and revealing 7 as the reference for stress. Cronbach’s α for the sample was 0.68. The five-item World Health Organization well-being index (WHO-5) has been used to measure depressive symptoms. A score < 13 should indicate further testing for depression (11); therefore, the standard cut-off score of < 13 was used. Cronbach’s α for the sample was 0.82. A four-item questionnaire on sleep disruption was designed for this study. The measure is on a five-point scale. A summary score was calculated and our SWEMWBS methodology used, yielding a mean of 10.0 (SD ¼ 3.07) and determining > 13 as the reference. Cronbach’s α for the sample was 0.73. The questionnaire was initially tested on university students and eight volunteers for cognitive interviewing. The wording of adaptations was checked.
SV Björnsdóttir et al
response rate by gender. Variables on mental health indicators were dichotomized. For comparison of variables of interest among people with C-CPD vs. controls, a logistic regression analysis was used to compute odds ratios (ORs) with 95% confidence intervals (CIs). With the same variables included, we further ran linear models, contrasting means of mental health indicators on a continuous scale between individuals with and without chronic pain. We observed similar results as in the logistic regression (data not shown). Backward selection was used to identify the best regression model to control for potential confounding factors in further analyses. The selected model included gender, age, monthly income, body mass index (BMI), smoking, and educational level. For weighting purposes, the final model also included the variable residence but the variable gender was excluded because of gender stratification. SPSS version 19 was used for the statistical analyses.
Results
Variables with missing values were completed with imputation, where imputation was likely to minimize systematic error due to answering styles (5). Potential confounding variables were categorized. Age was treated throughout the analyses in six categories as during sampling.
The data from the health survey contain responses from 2724 men and 3108 women (missing values on gender ¼ 74). Background characteristics of the study participants are presented in Table 1. In summary, our results indicate that the estimated prevalence of C-CPD is higher among women (24.7%) than men (15.2%), and increases with age (15.2% at 18–39 years, 27.7% at 60–79 years), decreased income [25.3% 200 000 Icelandic krona (IKR), 14.1% 370 000 IKR], less educational level (26.0% primary school, 13.6% university), and smoking (22.8% current or past smoker, 16.4% never smoked). Table 2 shows gender-stratified comparisons of selfassessed mental health, QoL, life satisfaction, stress, depressive symptoms, and sleep disruption in those reporting C-CPD vs. N-CPD in our population-based sample. Overall, higher odds of poor mental health and depressive symptoms were observed in individuals reporting C-CPD vs. N-CPD. In addition, higher odds of poor QoL, dissatisfaction with life, depressive symptoms, stress, and sleep disruption were observed. As fibromyalgia constitutes a distinct diagnostic entity from other chronic pain conditions, we repeated our main analyses without individuals reporting fibromyalgia. The results remained the same (data not shown) with the exception that, on excluding fibromyalgia, there was no difference in happiness between women reporting C-CPD and N-CPD [adjusted OR (ORadj ) 1.3, 95% CI 0.9–1.9].
Analytical strategy
Discussion
Weighted data analyses were applied to adjust the raw survey data to represent the population from which the sample was drawn. Population estimates are therefore based on weighted data to account for over-representation of older age groups in the sample and to adjust for uneven
The findings from our nationwide survey, using a randomly attained, stratified sample of nearly 5700 Icelanders, indicate that individuals with chronic musculoskeletal pain report deficient mental health. Both men and women with musculoskeletal chronic pain tend to be more
Chronic pain conditions The present survey included a question on chronic conditions, including items on chronic back pain, chronic neck symptoms, and fibromyalgia. The questions were stated individually, such as: Have you ever had fibromyalgia/chronic back pain/chronic symptoms in the neck? The response options were: yes now, yes but not now, no never. People reporting currently having any of these conditions met our criteria for current chronic pain disorder (C-CPD; n ¼ 1292). Those reported not having any of the conditions formed the reference population (non-chronic pain disorder, N-CPD; n ¼ 4464). Management of variables
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Mental health indicators to chronic pain
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Table 1. Characteristics of Icelanders reporting current chronic pain in December 2007, a self-completed sample of adults.
Prevalence in November to December 2007 Gender Men Women Age 18–39 years 40–59 years 60–79 years Marital status Living alone Living with partner Number of children No children One child 2 children Residence Capital area Country side Monthly income 200 000 IKR 201 000–369 000 IKR 370 000 IKR Social status Employed Unemployed Educational level Primary school (9–10 years) College/high school University Smoking Never smoked Current or past smoker Body mass index Current chronic pain No chronic pain
Chronic pain disorder
Chronic back pain
Chronic neck symptoms
Fibromyalgia
1292/5756 (19.9)
1022/5678 (16.2)
171/5667 (2.6)
369/5555 (5.3)
473/2673 (15.2) 807/3023 (24.7)
404/2636 (13.6) 608/2984 (19.0)
62/2632 (1.8) 108/2979 (3.4)
59/2594 (1.6) 306/2906 (9.2)
269/1669 (15.2) 438/1997 (21.2) 571/2031 (27.7)
236/1657 (13.6) 330/1977 (16.4) 446/1987 (21.9)
21/1661 (1.2) 73/1969 (3.6) 75/1982 (3.7)
51/1658 (2.4) 150/1950 (7.0) 164/1893 (8.7)
357/1482 (19.5) 921/4220 (19.9)
290/1459 (16.4) 722/4167 (16.1)
51/1455 (2.7) 119/4162 (2.6)
99/1431 (5.2) 265/4078 (5.3)
161/956 (14.4) 127/604 (18.9) 988/4125 (22.2)
140/945 (13.1) 109/602 (16.7) 761/4062 (17.4)
12/945 (1.0) 11/598 (1.5) 146/4058 (3.4)
32/938 (2.5) 25/593 (3.5) 305/3958 (6.9)
595/2735 (19.0) 671/2921 (21.3)
471/2702 (15.6) 534/2878 (17.4)
83/2701 (2.6) 80/2869 (2.5)
166/2652 (5.0) 193/2808 (6.0)
679/2403 (25.3) 334/1708 (18.3) 197/1309 (14.1)
534/2364 (20.9) 272/1692 (15.2) 159/1296 (11.3)
99/2352 (3.6) 37/1690 (2.2) 23/1298 (1.7)
216/2283 (7.6) 74/1664 (4.1) 45/1293 (3.1)
754/4078 (17.2) 481/1476 (30.2)
588/1033 (14.0) 393/1448 (25.1)
84/4038 (1.9) 76/1436 (5.1)
189/3988 (3.9) 159/1385 (10.6)
625/2260 (26.0) 270/1391 (17.2) 177/1251 (13.6)
502/224 (21.6) 220/1377 (14.5) 140/1241 (10.9)
79/2218 (3.4) 33/1378 (2.0) 20/1239 (1.6)
177/2153 (7.1) 71/1361 (4.1) 52/1230 (3.8)
426/2273 (16.4) 798/3166 (22.8)
327/2242 (13.2) 642/3127 (18.8)
60/2247 (2.4) 101/3116 (2.7)
122/2214 (4.1) 226/3049 (6.3)
27.8 5.5 26.4 4.7
27.6 5.4 26.5 4.8
27.9 6.4 26.6 4.8
28.9 5.7 26.5 4.8
IKR, Icelandic krona (local currency). Values given as n/N (%) or weighted mean SD, where n/N is the number/number in sample (population estimate), and population estimate is calculated through weight including gender, age, and residential area.
affected by perceived stress, depressive symptoms, sleep disruption, and life dissatisfaction than those without the condition. Our results support the hypothesis of a negative impact of chronic pain on mental health indicators, with our population-based data providing a realistic picture of mental health problems of individuals with chronic pain, in a naturalistic setting. This is indeed the first Icelandic study to provide in-depth information on the mental health status of people with chronic pain. Our observations that people with chronic pain conditions in a general population are subject to diminished QoL and well-being are in accordance with clinical studies on various chronic pain conditions (2–4, 12). Furthermore, in accordance with our results, Demyttenaere et al concluded that people in general populations reporting chronic pain problems also experience depression (and anxiety), independent of cultural or demographic origins (13). Notably, our findings indicate that men and women with chronic pain present with equally elevated ORs of mental health problems. Strengths of this study lie in the reasonable sample size of a representative sample from an underlying
population and the acceptable response rate. Initial studies further indicate that respondents were fairly similar to non-respondents in terms of age and population characteristics (5). The cross-sectional study design is an important limitation in this study, prohibiting inferences on the direction of associations observed. Information bias further constitutes a threat to the validity of data in studies relying on selfreports; in this study, individuals may, for example, either over- or under-report the measured mental health indicators. However, to distort the reported associations based on self-reports, individuals with chronic pain would need to have responded differently to the questionnaire from those not experiencing the condition. We have no indication for or against this claim, but caution is needed when interpreting the data. Finally, the diagnosis of chronic pain has been reported to lack validity (14) and the self-reported data of this study neither reflect an established diagnosis nor offer information on all conditions related to chronic widespread pain. These limitations should be
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Table 2. Self-assessed mental health indicators and quality of life (QoL) among adult individuals with and without current chronic pain. Women
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n/N (%) Poor mental health, in general No chronic pain Chronic pain Feeling unhappy (from the European Social Survey) No chronic pain Chronic pain Poor well-being and diminished QoL measured with the SWEMWBS No chronic pain Chronic pain Dissatisfaction with life measured with the SWLS No chronic pain Chronic pain Stress measured with the PSS No chronic pain Chronic pain Potential depression measured on the WHO-5 well-being index No chronic pain Chronic pain Sleeping disturbances measured with a self-designed questionnaire No chronic pain Chronic pain
OR
Men
adj
95% CI
n/N (%)
ORadj
95% CI
304/2205 (13.8) 257/800 (32.1)
1 2.4
1.9–3.0
353/2172 (16.3) 136/462 (29.4)
1 1.7
1.3–2.3
166/2136 (7.8) 108/778 (13.9)
1 1.6
1.2–2.2
191/2151 (8.9) 80/460 (17.4)
1 1.7
1.2–2.4
242/2093 (11.6) 135/734 (18.4)
1 1.6
1.2–2.1
253/2083 (12.1) 85/446 (19.1)
1 1.5
1.0–2.1
230/2120 (10.8) 177/766 (23.1)
1 2.0
1.5–2.6
281/2136 (13.2) 127/458 (27.7)
1 2.3
1.7–3.1
307/2110 (14.5) 171/765 (22.4)
1 1.7
1.3–2.2
243/2111 (11.5) 81/452 (17.9)
1 1.5
1.1–2.1
352/2119 (16.6) 256/769 (33.3)
1 2.4
1.9–3.0
308/2129 (14.5) 138/452 (30.5)
1 2.8
2.1–3.7
277/2067 (13.4) 237/762 (31.1)
1 2.8
2.2–3.5
180/2095 (8.6) 89/447 (19.9)
1 2.2
1.5–3.1
adj
OR , Odds ratio adjusted for age, monthly income, body mass index, smoking, educational level, and residential area; CI, confidence interval; SWEMWBS, Short Warwick–Edinburgh Mental Well-Being Scale; SWLS, Satisfaction With Life Scale; PSS, Perceived Stress Scale.
kept in mind when interpreting the results. As the Icelandic population is fairly homogeneous in terms of ethnicity and culture, caution should be exercised when generalizing findings to other populations. In our previous work we reported that individuals with chronic pain report various physical concerns and functional limitations (15) and our current study adds evidence that several mental health indicators are also applicable in this population. Together these studies provide a comprehensive picture of the global health symptomatology affecting individuals with chronic pain in the larger general population. We conclude that Icelanders in the general population who report chronic pain are subject to increased risk of declining mental health and diminishing QoL. Future research needs to focus on treatment and preventative measures of a decline in mental health among individuals with chronic pain.
Acknowledgements This project was funded by grants from the Association of Icelandic Physical Therapists and from the Lifelong Learning Centre in Southern Iceland. We thank the Public Health Institute for providing access to the data from the health survey.
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Mental health indicators to chronic pain
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