Sleep quality and hypertension: a counterfactual mediation analysis of the role of depressive symptoms.

Poor subjective sleep quality and moderate-to-severe depressive symptoms have both been associated with hypertension, but the extent to which depressive symptoms account for the sleep quality-hypertension association remains uncertain, particularly in community-based populations. This cross-sectional study analyzed data from 210,925 adults in the 2018 Korea Community Health Survey. Sleep quality was assessed with the Pittsburgh Sleep Quality Index and categorized as good or poor, while depressive symptoms were measured with the Patient Health Questionnaire-9 and dichotomized at a score of 10 to indicate moderate-to-severe depressive symptoms. Hypertension was defined as a self-reported physician diagnosis. Logistic regression models estimated associations between sleep quality, depressive symptoms, and hypertension, and counterfactual mediation analysis decomposed the association between poor sleep quality and hypertension into direct and indirect components, adjusting for sociodemographic, behavioral, and clinical factors. Poor sleep quality was associated with higher odds of hypertension (total effect odds ratio [OR], 1.119; 95% confidence interval [CI], 1.091-1.146). The natural direct effect remained significant after accounting for depressive symptoms (OR 1.106, 95% CI 1.078-1.133), whereas the natural indirect effect was statistically significant but small (OR 1.012, 95% CI 1.007-1.016), corresponding to a mediation proportion of 10.8% and 14.6% among non-employed participants. These findings suggest that poor subjective sleep quality was associated with hypertension and that moderate-to-severe depressive symptoms statistically accounted for only a modest proportion of the observed association. Because of the cross-sectional design, these findings should be interpreted as exploratory and hypothesis-generating rather than as evidence of temporal or causal relationships.