Sleep quality as a mediator of the relation between depression and chronic pain: a systematic review and meta-analysis

BackgroundChronic pain and depression represent two global health problems with considerable economic consequences. Although existing literature reports on the relation between depression and pain conditions, meta-analytic evidence backing the mediating role of sleep disturbance as one of the main symptoms of depression is scarce. To examine the extent to which sleep disturbance mediates the depression–chronic pain association, we conducted a systematic review and meta-analysis of the associations of chronic pain, depression, and sleep quality.MethodsWe systematically searched for literature in MEDLINE and other relevant databases and identified cohort and case–control studies on depression, sleep disturbance, and chronic pain. Forty-nine studies were eligible, with a total population of 120 489 individuals. We obtained direct and indirect path coefficients via two-stage meta-analytic structural equation modelling, examined heterogeneity via subgroup analyses, and evaluated primary studies quality.ResultsWe found a significant, partial mediation effect of sleep disturbance on the relation between depression and chronic pain. The pooled path coefficient (coef.) of the indirect effect was 0.03 (95% confidence interval [CI]: 0.01–0.05) and accounted for 12.5% of the total effect of depression on chronic pain. This indirect effect also existed for cohort studies (coef. 0.02; 95% CI: 0.002–0.04), European studies (coef. 0.03; 95% CI: 0.004–0.05), and studies that adjusted for confounders (coef. 0.04; 95% CI: 0.01–0.09).ConclusionsSleep disturbance partially mediates the association between depression and pain. Although plausible mechanisms could explain this mediation effect, other explanations, including reverse causation, must be further explored.Systematic review protocolPROSPERO CRD42022338201.