Sex differences in lifetime prevalence of low back pain: A multinational study of opposite‐sex twin pairs

Abstract

AbstractBackgroundLow back pain (LBP) is more likely to occur in people with a family history of this condition, highlighting the importance of accounting for familial factors when studying the individual risk of LBP. We conducted a study of opposite‐sex twin pairs investigating sex differences in LBP while accounting for (genetic and shared environmental) familial factors.MethodsWe applied a matched co‐twin control design to study 795 adult opposite‐sex pairs from Australia, Spain, and the United States (US). We used mixed‐effects logistic regression to assess the within‐pair association between female sex and lifetime prevalence of LBP in unadjusted and adjusted models for body‐mass‐index, and depression, as well as interactions between female sex and age (<median age vs. ≥median age) in this association.ResultsThe mean age of the sample was 47.4 years (Standard Deviation = 16.5). The adjusted odds ratio (aOR) of the association between sex and LBP in the merged sample was 1.11 (95% Confidence Interval = 0.88–1.40), with 87.4% of the variance in the studied association explained by between‐site heterogeneity (Q test; p = 0.001). Females had 2.37 (95% CI: 1.48–3.78) higher odds of LBP compared to their male co‐twins in the Spanish sample (adjusted), but a sex association was not found in the Australian nor US samples.ConclusionsWe found no evidence of the association between sex and LBP in our merged sample. Between‐population differences (i.e. cultural background or health system characteristics) are likely to be major factors leading to variation in the sex association with LBP when familial factors are accounted for.SignificanceOur study of adult opposite‐sex twin pairs found no evidence of an association between female sex and lifetime prevalence of low back pain after controlling for familial factors in the merged sample from Australia, Spain and USA, contrary to findings from previous studies of unrelated individuals. Our findings indicate potentially relevant between‐country genetic, cultural and environmental differences which may need to be considered for optimal and individualized strategies for the prevention and management of low back pain across the lifespan.