The Association Between Obesity and Low Back Pain and Disability Is Affected by Mood Disorders A Population-Based, Cross-Sectional Study of Men

Low back pain (LBP) and obesity are major public health problems; however, the relationship between body composition and low back pain in men is unknown. This study aims to examine the association between body composition and LBP and disability in a populationbased sample of men, as well as the factors that may affect this relationship. Nine hundred seventy-eight male participants from the Geelong Osteoporosis Study were invited to participate in a follow-up study in L. Brennan-Olsen, s), GCALL, BBS, FRACP, PhD emotional disorder was assessed using the Hospital Anxiety Depression Scale. Body composition was measured using dual energy x-ray absorptiometry. Of the 820 respondents (84% response rate), 124 (15%) had highintensity low back pain and/or disability (back pain). Low back pain was associated with higher body mass index (28.7 0.4 vs 27.3 0.2 kg/m, P1⁄4 0.02) and waist–hip ratio (0.97 0.006 vs 0.96 0.006, P1⁄4 0.04), with increased tendency toward having a higher fat mass index (8.0 vs 7.6 kg/m, P1⁄4 0.08), but not fat-free mass index (P1⁄4 0.68). The associations between back pain and measures of obesity were stronger in those with an emotional disorder, particularly for waist–hip ratio (P1⁄4 0.05 for interaction) and fat mass index (P1⁄4 0.06 for interaction). In a population-based sample of men, high-intensity LBP and/or disability were associated with increased levels of obesity, particularly in those with an emotional disorder. This provides evidence to support a biopsychosocial interaction between emotional disorders and obesity with low back pain. (Medicine 95(15):e3367) Abbreviations: BMI = body mass index, DXA = bone densitometry, FFM = fat-free mass, FFMI = fat-free mass index, FM = fat mass, FMI = fat mass index, GOS = Geelong Osteoporosis Study, HADS = Hospital Anxiety and Depression Scale, HADS-A = Hospital Anxiety and Depression Scale (anxiety subscale), HADS-D = Hospital Anxiety and Depression Scale (depression subscale), LBP = low back pain. INTRODUCTION L ow back pain is a major public health problem and was identified as the leading cause of disability worldwide in the Global Burden of Disease Study. Approximately 80% of adults experience at least 1 episode of back pain during their lifetime. Despite the magnitude of the problem, the structural origin of most episodes of back pain is unknown, with poor correlation between symptoms and structural abnormalities. Hence back pain is usually considered ‘‘non-specific.’’ In order to address this problem, research has focused on identifying modifiable risk factors for back pain. Potential risk factors for back pain include older age, female sex, lower educational attainment, increased physical work demands, and emotional disorders. Obesity has also been linked with low back pain, although a previous systematic ity was only a weak risk factor. It is imately one-third of the world’s adult ight, as defined by body mass index www.md-journal.com | 1 (BMI). Obesity may have both biomechanical and metainflammatory effects on the spine. However, obesity measured by BMI is a crude measure of adiposity, as it fails to differentiate fat from fat-free mass. Moreover, body composition is markedly different between males and females, with higher fat mass in females compared with males. This may account for the results of a meta-analysis that concluded that the association between being overweight or obese and low back pain is stronger in women compared with men. While this gender disparity in the relationship between obesity and back pain may be related to differences in pain perception and hormonal influences, differences in the composition of fat and fat-free mass between males and females may also play a role. Fat mass has been shown to be associated with back pain intensity and disability in a cohort of predominantly female adults, but this has yet to be comprehensively examined in males. This is a particularly pertinent question since the burden of low back pain in men is estimated to be higher than in women, as measured by disability-adjusted life years. The aim of this study was to examine the association between body composition and low back pain and disability in a population-based sample of men, as well as the factors that may affect this relationship.