Relationship Between Mental Health and Foot Pain

Transcription

1 Arthritis Care & Research Vol. 66, No. 8, August 2014, pp DOI /acr , American College of Rheumatology BRIEF REPORT Relationship Between Mental Health and Foot Pain PAUL A. BUTTERWORTH, 1 DONNA M. URQUHART, 2 FLAVIA M. CICUTTINI, 2 HYLTON B. MENZ, 3 BOYD J. STRAUSS, 2 JOSEPH PROIETTO, 4 JOHN B. DIXON, 5 GRAEME JONES, 6 AND ANITA E. WLUKA 2 Objective. Although mental health is related to the persistence of musculoskeletal pain, our understanding of the relationship between mental health and foot pain is limited. Subsequently, we conducted a 3-year longitudinal study to examine the relationship between mental health and foot pain in a community-based population. Methods. Eighty-three community-dwelling participants (mean SD body mass index [BMI] kg/m 2 ) who had foot pain at study inception in 2008 and for whom measures of mental health (Short Form 36 [SF-36] health survey mental component summary [MCS]) were available, were invited to take part in this followup study in Change in foot pain was determined by the difference between the Manchester Foot Pain and Disability Index score at baseline and followup; therefore, a decrease in the score indicated improved foot pain and an increase indicated deterioration in foot pain. Linear regression was used to determine the factors affecting change in foot pain. Results. Of the 62 respondents (75% response rate, 49 women and 13 men), there were 27 (44%) whose foot pain deteriorated. A higher MCS score of the SF-36 health survey at baseline was associated with a slower progression of foot pain ( coefficient 0.29, 95% confidence interval 0.42, 0.01), adjusted for age, sex, BMI, and physical health. Conclusion. Mental health is associated with changes in foot pain. Clinicians dealing with this population should consider the contribution of mental health in their management and treatment of foot pain. Introduction Foot pain and deformity have been recognized as independent risk factors for locomotor disability, diminished balance, and an increased risk of falling. In addition, foot pain impairs functional activities of daily living among older adults, impacting negatively on health-related quality of life (1). Several risk factors for foot pain have been identified, including increased age, female sex (1), and obesity (2). Although poor mental health has been identified as a predictor of chronic joint pain (3), the association between mental health and foot pain has only been shown in crosssectional analyses (1,4,5). There are a number of possible mechanisms that may link mental health and foot pain. First, chronic pain may be a symptom or a manifestation of mental health disorders, such as depression (6). Alternatively, muscle atrophy may be associated with negative affect (e.g., activity avoidance) and chronic joint pain. The avoidance of painrelated activity theory suggests that people with osteoarthritis avoid activity that induces short-term pain. As a consequence of avoiding activity, patients develop muscle Supported by the National Health and Medical Research Council (grant ), Monash University, Shepherd Foundation, and Royal Australasian College of Physicians. Mr. Butterworth s work was supported by an Australian Postgraduate Award. Dr. Urquhart s work was supported by a National Health and Medical Research Council Career Development Fellowship ( ). Dr. Menz s work was supported by a National Health and Medical Research Council Senior Research Fellowship ( ). Dr. Wluka s work was supported by a Senior Postdoctoral Fellowship, Monash University. Dr. Dixon s work was supported by a National Health and Medical Research Council Senior Research Fellowship (10497). 1 Paul A. Butterworth, BPod, MPod, FACPS: La Trobe University, Bundoora, Victoria, Australia, and Southern Cross University, Bilinga, Queensland, Australia; 2 Donna M. Urquhart, BPhysio(Hons), PhD, Flavia M. Cicuttini, MBBS, FRACP, PhD, Boyd J. Strauss, MBBS, FRACP, PhD, Anita E. Wluka, MBBS, FRACP, PhD: Monash University, Melbourne, Victoria, Australia; 3 Hylton B. Menz, PhD: La Trobe University, Bundoora, Victoria, Australia; 4 Joseph Proietto, MBBS, FRACP, PhD: University of Melbourne and Austin Health Melbourne, Melbourne, Victoria, Australia; 5 John B. Dixon, MBBS, FRACGP, FRACP, Edin PhD: Baker IDI Heart and Diabetes Institute and Alfred Hospital, Melbourne, Victoria, Australia; 6 Graeme Jones, MBBS, FRACP, MD: Menzies Research Institute, Hobart, Tasmania, Australia. Address correspondence to Anita E. Wluka, MBBS, FRACP, PhD, School of Public Health and Preventive Medicine, Monash University, Alfred Centre, Commercial Road, Melbourne, Victoria 3004, Australia. anita.wluka@ monash.edu. Submitted for publication July 21, 2013; accepted in revised form January 21,

2 1242 Butterworth et al Significance & Innovations Poor mental health and foot pain have been associated in cross-sectional studies. Whether mental health affects the outcome of foot pain is not known. We demonstrated a relationship between mental health and change in foot pain over 3 years, such that higher mental health scores were associated with a slower progression in foot pain. atrophy and subsequent joint instability, leading to increased tissue stress and chronic pain (7). Consequently, to understand the temporal relationship between mental health and foot pain, it is necessary to examine this relationship with longitudinal analysis. Therefore, the aim of this study was to examine the relationship between mental health and foot pain, over 3 years, in a community-based population. Patients and methods Study population. Participants (n 83) from a baseline study (in 2008) who had foot pain according to the Manchester Foot Pain and Disability Index (MFPDI) (8), and for whom measures of mental health (mental component summary [MCS] of the Short Form 36 [SF-36] health survey) were available were eligible for the current study. Participants were invited to complete the MFPDI 3 years later. Of these, 62 (75%) completed the followup study. All participants lost to followup were unable to be contacted by the researchers. Participants (ages years, n 136) were initially recruited from a community-based population through the local media and public, private, and community weightloss clinics. Participants were asked to participate in a study of the relationship between obesity and musculoskeletal disease, without regard to the presence or absence of foot pain. Initial inclusion and exclusion criteria have been previously published (9). The aim of the baseline cross-sectional research was to examine the relationship between body composition and foot pain in a population ranging from healthy to obese. The study was approved by the Alfred Human Research and Ethics Committee (HREC), the Monash Standing Research Ethics Committee, the Austin Health HREC, and the University of Melbourne Central HREC. Informed consent was obtained from all participants. Data collection. The MFPDI was used to document disabling foot pain at baseline (2008) and followup (2011). The MFPDI is a validated measure previously used to determine the prevalence of disabling foot pain in populationbased studies (4). The MFPDI consists of 19 items that are preceded with the phrase,... because of pain in my feet, and formalized under 4 categories as follows: functional limitation (10 items), pain intensity (5 items), personal appearance (2 items), and difficulties with work or leisure activities (2 items). Each item is documented as being present none of the time (0 points), on some days (1 point), or on most/every day (2 points); subsequently, scores on the MFPDI range between 0 38, with higher scores indicating worse foot pain. In longitudinal analysis, a reduction in the MFPDI score indicates improvement in foot pain and an increase suggests deterioration or worsening of pain (10). The SF-36 is a self-reported measure. It was used at baseline to assess health-related quality of life. The SF-36 has 8 standard domain scores: physical function, physical role, pain, general health, vitality, social functioning, emotional role, and mental health. Components of each of the 8 domain scores are combined in a weighted manner (positive and negative) to develop the validated physical component summary (PCS) and the MCS scores (11). These summary scores are adjusted to provide population normal values of 50 and an SD of 10 (12). Low MCS scores indicate poorer mental health and low PCS scores indicate decreased physical health. Measures of obesity taken at the time of the baseline MFPDI were used in the current analysis. Weight was measured to the nearest 0.1 kg (shoes, socks, and bulky clothing were removed). Height at baseline was measured to the nearest 0.1 cm (shoes and socks were removed) using a stadiometer. From these data, body mass index (BMI) was calculated and reported in kg/m 2. Statistical analysis. Independent-samples t-tests and chi-square tests were used to assess differences in those with foot pain at baseline whose pain improved (change in MFPDI 0) or deteriorated (change in MFPDI 0). Change in foot pain was determined by the difference between the MFPDI score at baseline and followup; therefore, a decrease in the MFPDI score indicated improved foot pain and an increase indicated deterioration in foot pain. Linear regression was used to assess the relationship between mental health and change in foot pain, and the multivariate analyses were adjusted for age, sex, BMI, PCS, and MCS. P values less than 0.05 (2-tailed) were regarded as statistically significant. All analyses were performed using the SPSS statistical package (standard version 18.0). Results Sixty-two (75%) of 83 eligible participants with foot pain at baseline completed this study. Of the 62 participants (mean SD age years, range years), 49 (79%) were women who ranged from normal weight to morbidly obese (mean SD BMI kg/m 2, range kg/m 2 ). Of the 21 participants who were lost to followup, 15 (71%) were women, were of similar mean SD age ( years), and had a comparable mean SD BMI ( kg/m 2 ), MCS ( ), and baseline MFPDI score ( ) relative to those who completed the followup study. There were 27 (44%) participants whose foot pain deteriorated. The characteristics of the study participants are presented in Table 1. Change in mean SD pain scores ( ) approximated the normal distribution and ranged between 30

3 Mental Health and Foot Pain 1243 Table 1. Participant characteristics* Foot pain improved (n 35) Foot pain deteriorated (n 27) P Age, years Female sex, no. (%) 27 (77) 22 (81) 0.68 BMI, kg/m Baseline MFPDI score PCS MCS SF-36 domain scores Physical function Physical role Pain General health Vitality Social functioning Emotional role Mental health * Values are the mean SD unless otherwise indicated. BMI body mass index; MFPDI Manchester Foot Pain and Disability Index; PCS physical component summary of the Short Form 36 (SF-36) health survey; MCS mental component summary of the SF-36. Includes 2 participants whose scores remained unchanged. Calculated for difference between subjects with stable and deteriorating foot pain using independentsamples t-test unless otherwise indicated. Calculated for difference between subjects with stable and deteriorating foot pain using chi-square test. and 16. For those participants whose foot pain improved (median 4), changes in pain scores ranged from 0 to 30. In those participants whose foot pain deteriorated, pain scores (median 5) ranged from 1 to 16. When those with improved and deteriorating foot pain were compared (Table 1), those with improved foot pain had a significantly higher baseline MCS score than those whose pain deteriorated (P 0.02). The baseline impairment in the PCS for both groups was similar and the domain pain scores were the same. Within the MCS, the only SF-36 domain to differ significantly between those with improved foot pain compared to those whose pain deteriorated was vitality, being significantly higher (P 0.02) in those with improved foot pain (Table 1). In the multivariate analysis, age, sex, BMI, and PCS were not associated with change in foot pain. However, a small association was shown between a higher baseline MCS ( coefficient 0.29, 95% confidence interval 0.42, 0.01) and a slower progression in foot pain, adjusted for age, sex, BMI, and PCS (Table 2). Discussion This study aimed to examine the relationship between mental health and foot pain in a community-based population. Our findings indicate that mental health at baseline, assessed using the MCS of the SF-36 health survey, was higher in adults whose foot pain improved and was associated with changes in foot pain over a 3-year period. Two cross-sectional studies have examined and shown a relationship between mental health and foot pain. The first showed the MFPDI and its subscales (functional limitation, pain intensity, and concern about appearance) to Table 2. Regression coefficients for the association between baseline predictors with change in foot pain over 3 years among 62 men and women with baseline foot pain* Change in foot pain Univariate coefficient (95% CI) P Multivariate coefficient (95% CI) P Age 0.08 ( 0.20, 0.37) ( 0.17, 0.40) 0.43 Sex 0.03 ( 6.74, 5.30) ( 9.80, 3.30) 0.32 BMI 0.03 ( 0.32, 0.26) ( 0.35, 0.31) 0.90 SF-36 MCS 0.23 ( 0.34, 0.02) ( 0.42, 0.01) 0.04 SF-36 PCS 0.05 ( 0.18, 0.27) ( 0.26, 0.27) 0.97 * 95% CI 95% confidence interval; BMI body mass index; SF-36 Short Form 36 health survey; MCS mental component summary; PCS physical component summary. Adjusted for age, sex, BMI, MCS, and PCS.

4 1244 Butterworth et al be significantly associated with scores on the Goldberg Anxiety and Depression Scale and the mental health components of the SF-36 (4). The second study, in a crosssectional analysis of 3,206 people, demonstrated that people with foot pain had lower scores for not only the mental health components of the SF-36, but also the physical and bodily pain components after adjustment for age, sex, and BMI (1). In the current study, the PCS scores did not differ between groups and were not a significant predictor in regression analysis; this may suggest that the MCS plays a more significant role in changes in foot pain. An interesting finding from this current study was that the mean MCS score for the improved foot pain group was within the range considered to be normal, according to Australian population estimates at baseline; conversely, the deteriorating foot pain group had a mean MCS value that was well below Australian population norms (12,13). Our findings are the first longitudinal data to demonstrate a relationship between mental health and change in foot pain. The only previous longitudinal study showed that self-reported depression in elderly women was associated with foot pain at baseline but not at followup (5). The findings of the current study are consistent with previous studies that reported mental health to be a significant predictor of the outcome of chronic joint pain (3). This study supports the theory that the outcome of foot pain may be affected by a person s mental health status. Therefore, those with worse mental health are less likely to show improvement in pain. Although the limbic system moderates the amount of pain experienced (emotional pain) for any given noxious stimulus, the psychosomatic response to the stimulus varies between individuals. This may explain why preexisting psychological factors have been shown to influence the development of chronic pain conditions (3,14). Therefore, the results from this current study suggest that foot pain could be related to mental health in the same manner as other chronic musculoskeletal conditions. However, it is also possible that being in a state of chronic pain may cause negative affect, such as activity avoidance, which may perpetuate the persistence of pain. As we did not know how long the participants had foot pain prior to their involvement in this study, we were unable to draw any conclusions on the relationship between negative affect and foot pain. Consequently, further studies will be required to determine whether mental health is a cause or a consequence of foot pain. Our study was limited in that there is currently no established measure of minimally significant change using the MFPDI (15). Furthermore, we did not use instruments designed to measure specific mental conditions or include known clinical diagnosis of mental illness in our study. In addition, weight change may have been a relevant mediator of the change in foot pain, and low MCS baseline scores may have been associated with weight loss or gain over the 3-year period. Whether the results from this study can be generalized to men is unknown, as our study had few male participants. Nevertheless, while there are sex differences in pain perception (9), the results of our analysis were similar when limited to women only (data not shown). Furthermore, we did not evaluate other variables that may contribute to foot pain, such as foot structure and function. The key strengths of this study were the use of an established and validated measure of foot pain (the MFPDI) and the longitudinal design, which allowed us to examine the temporal relationship between mental health and foot pain. This study demonstrated that 1) baseline MCS is higher in those whose pain improved versus those whose pain got worse over 3 years, and 2) a higher baseline MCS is associated with a slower progression in foot pain over 3 years. Clinicians treating foot pain should consider the patient s mental health in their management, consistent with their management of other chronic musculoskeletal conditions. AUTHOR CONTRIBUTIONS All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be submitted for publication. Dr. Wluka had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study conception and design. Butterworth, Cicuttini, Menz, Strauss, Dixon, Jones, Wluka. Acquisition of data. Butterworth, Cicuttini, Strauss, Proietto, Wluka. Analysis and interpretation of data. 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