Sex differences in the association of metabolic syndrome with low back pain among middle-aged Japanese adults: a large-scale cross-sectional study

BACKGROUND: Although some recent studies have indicated an association between metabolic syndrome (MetS) and musculoskeletal disease, little is known about the association of MetS with low back pain (LBP). The present study aimed to investigate sex differences in the association of MetS and the clustering of MetS components with LBP among middle-aged Japanese individuals. METHODS: Study subjects were 45,192 adults (30,695 men, 14,497 women) aged 40–64 years who underwent annual health checkups conducted from April 2013 to March 2014. MetS was defined according to the criteria of the Examination Committee of Criteria for MetS in Japan as abdominal obesity plus at least two of dyslipidemia, high blood pressure, or high blood glucose. Information on LBP and health-related lifestyles were collected using a self-administered questionnaire. Logistic regression modeling was used to calculate the odds ratio (OR) and 95% confidence interval (CI) for LBP. RESULTS: After adjusting for age and lifestyle factors, the OR of MetS for LBP was 1.15 (95% CI 0.95–1.40) in men and 2.16 (95% CI 1.32–3.53) in women. Compared to subjects without abdominal obesity, the presence of abdominal obesity significantly increased the OR for LBP among men (abdominal obesity only: OR 1.34, 95% CI 1.02–1.76; abdominal obesity plus one component: OR 1.24, 95% CI 1.01–1.52; abdominal obesity plus two or more components: OR 1.26, 95% CI 1.02–1.55). Among women, adding other components of MetS to abdominal obesity significantly increased ORs for LBP (abdominal obesity only: OR 1.70, 95% CI 0.94–3.08; abdominal obesity plus one component: OR 1.66, 95% CI 1.06–2.60; abdominal obesity plus two or more components: OR 2.30, 95% CI 1.41–3.78). CONCLUSIONS: This large-scale cross-sectional study indicated that MetS was significantly associated with LBP among women only and that a sex-difference existed in the association between the clustering of MetS components and LBP. Clustering of MetS components by sex may need to be considered for the prevention of LBP, although further prospective studies are needed to clarify the causality.