Does sedentary behavior increase the risk of low back pain? A population-based co-twin study of Spanish twins.

BACKGROUND The relationship between sedentary lifestyle and low back pain (LBP) remains unclear and previous research has not accounted for genetic and early environmental factors. PURPOSE Our aim was to investigate if sedentary behavior is associated with the lifetime prevalence of persistent LBP and the risk of developing persistent LBP, care-seeking due to LBP, and activity limiting LBP when genetics and early environmental factors are accounted for. STUDY DESIGN Both cross-sectional and longitudinal designs with a within-pair twin case-control were implemented. PATIENT SAMPLE There were 2,148 twins included in the cross-sectional analysis whereas 1,098 twins free of persistent LBP at baseline were included in the longitudinal analysis. OUTCOME MEASURES Sedentary behavior was the explanatory variable. Lifetime prevalence of LBP was the outcome variable in the cross-sectional analysis. The incidence of persistent LBP, care-seeking due to LBP, and activity limiting LBP were the outcome variables for the longitudinal analysis. METHODS This observational study was supported by a grant in 2012. No competing interests were declared. RESULTS In the cross-sectional analysis, sedentary behavior was slightly associated with an increased prevalence of persistent LBP in females but not in males. This association was not apparent when genetics and early environmental factors were accounted for. We acknowledge that the small sample included in the co-twin analyses have yielded wide confidence intervals, and that caution should be exercised when interpreting and an association may not be ruled out. In the longitudinal analysis, sedentary behavior did not significantly increase the risk of persistent LBP, care-seeking due to LBP, or activity limiting LBP. CONCLUSIONS Sedentary behavior is associated with concurrent LBP. However, this association is weak; it only appears in females and decreases when accounting for genetics. Future studies using a twin design with larger samples should be conducted to further test these findings.