American Journal of Epidemiology ª The Author 2009. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oxfordjournals.org. Vol. 171, No. 2 DOI: 10.1093/aje/kwp356 Advance Access publication: December 11, 2009 Meta- and Pooled Analyses The Association Between Obesity and Low Back Pain: A Meta-Analysis Rahman Shiri*, Jaro Karppinen, Pa ¨ ivi Leino-Arjas, Svetlana Solovieva, and Eira Viikari-Juntura * Correspondence to Dr. Rahman Shiri, Centre of Expertise for Health and Work Ability, Finnish Institute of Occupational Health, Topeliuksenkatu 41 a A, FIN-00250 Helsinki, Finland (e-mail: rahman.shiri@ttl.fi). Initially submitted June 15, 2009; accepted for publication October 5, 2009. This meta-analysis assessed the association between overweight/obesity and low back pain. The authors systematically searched the Medline (National Library of Medicine, Bethesda, Maryland) and Embase (Elsevier, Amsterdam, the Netherlands) databases until May 2009. Ninety-five studies were reviewed and 33 included in the meta-analyses. In cross-sectional studies, obesity was associated with increased prevalence of low back pain in the past 12 months (pooled odds ratio (OR) ¼ 1.33, 95% confidence interval (CI): 1.14, 1.54), seeking care for low back pain (OR ¼ 1.56, 95% CI: 1.46, 1.67), and chronic low back pain (OR ¼ 1.43, 95% CI: 1.28, 1.60). Compared with nonoverweight people, overweight people had a higher prevalence of low back pain but a lower prevalence of low back pain compared with obese people. In cohort studies, only obesity was associated with increased in- cidence of low back pain for 1 day in the past 12 months (OR ¼ 1.53, 95% CI: 1.22, 1.92). Results remained consistent after adjusting for publication bias and limiting the analyses to studies that controlled for potential confounders. Findings indicate that overweight and obesity increase the risk of low back pain. Overweight and obesity have the strongest association with seeking care for low back pain and chronic low back pain. incidence; overweight; prevalence; publication bias; referral and consultation Abbreviation: BMI, body mass index. Obesity is a growing public health concern. Globally, the number of overweight or obese people is dramatically increasing (1). Obesity contributes substantially to the bur- den of chronic medical conditions, and these medical con- ditions place a high economic burden on the health care systems (1). Low back pain is also a common health problem (2). It is a common cause of work-related disability and sickness absence (3). In the general population, the 1-month preva- lence of low back pain ranges from 30% to 40% (3, 4); the annual prevalence of low back pain ranges from 25% to 60% (3–5) and of chronic low back pain from 10% to 13% (6, 7). Low back pain is more common in women than in men (4, 8). The association between obesity and low back pain re- mains controversial. Few reviews on the relation between obesity and low back pain have been published so far. Five of them were nonsystematic, including only 6–8 studies (9–12) or only studies published between 2000 and March 2006 (13). The only known systematic review reported inconsistent results regarding the link between weight- related factors and low back pain (14). None of these reviews performed a meta-analysis or reported evidence of a temporal relation between obesity and low back pain. Our aim was to provide a systematic literature review of the association between overweight/obesity and low back pain and to estimate the magnitude of such an asso- ciation using meta-analysis. To address causality of asso- ciations, cross-sectional and cohort studies were analyzed separately. MATERIALS AND METHODS Search strategy Studies of interest were identified by searches of the Med- line (National Library of Medicine, Bethesda, Maryland) and Embase (Elsevier, Amsterdam, the Netherlands) data- bases from 1966 until May 2009 using predefined keywords (Web Table 1; this information is described in the first of 135 Am J Epidemiol 2010;171:135–154 by guest on May 11, 2011 aje.oxfordjournals.org Downloaded from