Does sleep quality modify the relationship between common mental disorders and chronic low back pain in adult women?

This study explored the association between common mental disorders (CMD) and chronic low back pain (CLBP) in women, while considering poor sleep quality as a potential effect modifier of this relationship.

A cross-sectional population-based study was conducted with a representative sample of 1068 women (age 20-69 years) living in the urban area of São Leopoldo, RS, Brazil. CLBP was defined as pain lasting for ≥3 months; CMD was assessed using the Self-Reporting Questionnaire (SRQ-20; score ≥8); poor sleep quality was evaluated using the Pittsburgh Sleep Quality Index (PSQI; score ≥5). Poisson regression with robust variance was used to estimate the prevalence ratios (PR) with 95% confidence intervals (CI).

The prevalence of CLBP, CMD, and poor sleep quality was 46.8% (95% CI: 43.8-49.8), 33.5% (95% CI: 30.3-36.3), and 42.3% (95% CI: 39.3-45.2), respectively. Poor sleep quality was a significant modifier of the association between CMD and CLBP. Among women with poor sleep quality, women with CMD had a 48% higher probability of having CLBP compared to women without CMD and after adjustment for confounders (PR = 1.48; 95% CI: 1.23-1.77; p < 0.001). The relationship between CMD and CLBP was not statistically significant in women with good sleep quality.

This study revealed a significant relationship between CMD and CLBP, wherein poor sleep quality acted as an effect modifier. Women with CMD and poor sleep quality were more vulnerable to CLBP.