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

Objective: 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.

Methods: 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).

Results: 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.

Conclusions: 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.