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OBSERVATIONAL STUDY

Relationships Between Weight, Physical Activity, and Back Pain in Young Adult Women Sharmayne R.E. Brady, MBBS, BMedSc, FRACP, Sultana Monira Hussain, MBBS, MPH, PhD, Wendy J. Brown, BSc, GDipPhysEd, MSc, PhD, FASMF, FACSM, Stephane Heritier, BSc, MSc, MBA, PhD, Baki Billah, BSc, MSc, MAS, PhD, Yuanyuan Wang, MBBS, MMed, MD, PhD, Helena Teede, MBBS, FRACP, PhD, Donna M. Urquhart, BPhysio, PhD, and Flavia M. Cicuttini, MBBS, PhD, MSc DLSHTM, FRACP, FAFPHM

Abstract: Back pain causes enormous financial and disability burden worldwide, which could potentially be reduced by understanding its determinants to develop effective prevention strategies. Our aim was to identify whether modifiable risk factors, weight and physical activity, are predictive of back pain in young adult women. Women born between 1973 and 1978 were randomly selected from the national health insurance scheme database to participate in The Australian Longitudinal Study of Women’s Health. Self-reported data on back pain in the last 12 months, weight, height, age, education status, Editor: Ediriweera Desapriya. Received: January 25, 2016; revised: March 17, 2016; accepted: March 21, 2016. From the Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Melbourne, Victoria (SREB, SMH, SH, BB, YW, DMU, FMC); School of Human Movement and Nutrition Sciences, University of Queensland, St. Lucia, Queensland (WJB); Monash Center for Health Research and Implementation, School of Public Health and Preventive Medicine, Monash University (HT); and Diabetes and Vascular Medicine Unit, Monash Health, Melbourne, Victoria, Australia (HT). Correspondence: Professor Flavia Cicuttini, Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Alfred Hospital, Melbourne, Victoria 3004, Australia (e-mail: [email protected]). SREB 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. SREB was also responsible for writing and editing the manuscript. SMH assisted in data analysis, editing, and review of manuscript. WJB was responsible for data collection and acquisition, contributed to study conception and the analysis plan, provided editing assistance and review of the manuscript. SH and BB assisted with statistical analysis and editing of the manuscript. YW assisted with editing and review of manuscript. HT contributed to study conception, provided editing assistance and review of the manuscript. DMU provided editing assistance and review of the manuscript. FMC contributed to study conception, data analysis, editing, and review of manuscript. All authors gave final approval of the submitted version of the manuscript. SREB is supported by a National Health and Medical Research Council (NHMRC) Clinical Postgraduate Research scholarship (No. 1074979). SMH is the recipient of the AFA-ARA Heald fellowship funded by Arthritis Australia foundation. HT is supported by an NHMRC Practitioner Fellowship 1942516. YW and DMU are the recipients of NHMRC Career Development Fellowships (Clinical Level 1 No. 1065464 and Clinical Level 1 No. 1011975, respectively). Research on which this article is based was conducted as part of the Australian Longitudinal Study on Women’s Health, the University of Newcastle and the University of Queensland. The authors report no conflicts of interest. Copyright # 2016 Wolters Kluwer Health, Inc. All rights reserved. This is an open access article distributed under the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ISSN: 0025-7974 DOI: 10.1097/MD.0000000000003368

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physical activity, and depression were collected in 2000, 2003, 2006, 2009, and 2012. In 2000, 9688 women completed the questionnaire and 83% completed follow-up 12 years later. At baseline, median age was 24.6 years and 41% had self-reported back pain. For every 5 kg higher weight at baseline, there was a 5% (95% confidence interval [CI] 4%–6%) increased risk of back pain over the next 12 years. Higher weight at each survey also predicted back pain risk 3 years later (P < 0.001). The effects of weight on back pain were most significant in those with BMI 25 kg/m2 and were observed at all levels of physical activity. Inadequate physical activity and depression were independent predictors of back pain over the following 12 years (both P < 0.001), after adjusting for age, weight, height, and education status. Back pain is common in community-based young adult women. Higher weight, inadequate levels of physical activity, and depression were all independent predictors of back pain over the following decade. Furthermore, the adverse effects of weight on back pain were not mitigated by physical activity. Our findings highlight the role of both higher weight and physical inactivity in back pain among young women and suggest potential opportunities for future prevention. (Medicine 95(19):e3368) Abbreviations: ALSWH = Australian Longitudinal Study of Women’s Health, BMI = Body mass index, GEE = Generalized estimating equations, MET = Metabolic Equivalent, WHO = World Health Organization.

INTRODUCTION

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ack pain is a major global health problem, causing greater disability worldwide than any other condition.1 The total costs of back pain in the United States of America have been estimated to exceed $100 billion USD per year, with much of these costs being attributed to indirect costs, such as lost wages and reduced productivity.2 Not only is back pain associated with significant economic burden3 and major disability, but therapeutic options also have limited efficacy.4 Hence, clarifying predictors of back pain is important to optimize preventive strategies. Furthermore, as previous episodes of back pain are predictive of future recurrence,5,6 understanding risk factors associated with back pain in early adulthood is particularly important. There is a lack of scientific consensus about the root causes of back pain, and there is poor correlation between back pain and spinal imaging.7 There are several potential risk factors for back pain that have been previously www.md-journal.com |

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described, including female sex, white ethnicity, age, and psychological factors.8 Not only are women in many studies more likely to suffer from back pain,9 – 11 they also have been reported to utilize health care to a greater extent than men.12,13 However, few studies in younger women have addressed potentially modifiable risk factors for back pain, such as obesity and physical activity. In a prospective study of the 1958 British birth cohort, self-reported obesity in women at age 23 increased the incidence of back pain 10 years later (adjusted odds ratio [OR] 1.78).14 However, in a subsequent article based on this cohort, obesity was not a risk factor for incident back pain from 32 to 33 years of age.15 Other cohort studies of young adolescent twins16 and young adults without back pain17 have shown either no or minimal association between overweight or obesity and nonspecific back pain several years later. Similarly, in recent metaanalyses, although cross-sectional studies have reported associations between obesity and back pain, there is a lack of longitudinal data to support a temporal relationship.18,19 Physical activity may also have a role in back pain, but to date, prospective studies examining its relationship with back pain have yielded inconsistent results17,20 with none addressing this question in young community-based women in systematic reviews.21,22 Thus, the aim of this study was to determine whether weight and physical activity predict future back pain in young women over a 12-year period, in a large population-based cohort study.

METHODS Participants The Australian Longitudinal Study of Women’s Health (ALSWH) first collected mailed survey data from 3 age cohorts of Australian women in 1996 (young women 1973–1978; middle-aged women 1946–1951; older women 1921–1926). Participants were randomly selected from the national health insurance scheme (Medicare) database (which includes most permanent residents of Australia) with intentional oversampling from rural and remote areas.23,24 The women in each cohort have completed surveys at 3-year intervals since 2000. The surveys included questions about a diverse range of issues including health behaviors, health service use, and physical and mental health, as well as social and demographic factors. The young cohort, born between 1973 and 1978, was surveyed in 1996, 2000, 2003, 2006, 2009, and 2012. The present study analyzed data collected from the second survey in year 2000 (because important variables were available in this survey that were not included in the 1996 survey) through to the sixth survey in 2012. Figure 1 shows the numbers and proportions of women who answered a specific question on back pain. Further details of the methods used and sample characteristics have been reported elsewhere23,24 and are available on the ALSWH website (www.alswh.org.au). Women who were identified as being currently pregnant at the time of any of the 5 surveys (n ¼ 3010) were excluded from this longitudinal analysis. The Human Research Ethics Committees of the University of Newcastle and the University of Queensland approved the study methods. Written informed consent was obtained from all participants.

Back Pain At each survey, women were asked ‘‘In the last 12 months have you had back pain?’’ They were asked to circle one

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Survey response rate

Baseline (2000)-9,688 answered survey (9,671 answered back pain queson)

100%

Follow-up 1 (2003) - 9,081 answered survey (9,056 answered back pain queson)

94%

Follow-up 2 (2006) - 9,145 answered survey (9,088 answered back pain queson)

94%

Follow-up 3 (2009) - 8,200 answered survey (8,091 answered back pain queson)

85%

Follow-up 4 (20012) - 8,010 answered survey (7,955 answered back pain queson)

83%

FIGURE 1. Numbers of women who answered the back pain question at each survey from 2000 to 2012.

response, which related to the frequency of their back pain: ‘‘never,’’ ‘‘rarely,’’ ‘‘sometimes,’’ or ‘‘often.’’ They were also asked ‘‘Did you seek help for this problem?’’ Participants were asked to circle either ‘‘Yes’’ or ‘‘No.’’ Those who responded ‘‘never’’ or ‘‘rarely’’ having back pain were categorized as ‘‘no back pain,’’ whereas those who responded ‘‘sometimes’’ or ‘‘often’’ were categorized as ‘‘back pain.’’

Obesity Body mass index (BMI) was calculated at each survey from self-reported height and weight and classified as underweight or healthy weight (BMI

Relationships Between Weight, Physical Activity, and Back Pain in Young Adult Women.

Back pain causes enormous financial and disability burden worldwide, which could potentially be reduced by understanding its determinants to develop e...
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