Objective: Cross-sectional studies suggest a strong association between depression and restless legs syndrome (RLS); however, the temporal relationship between the two disorders remains unknown. We tested whether the presence of clinically relevant depressive symptoms (CRDS) is a risk factor for subsequent RLS in the general population. The relationship between prevalent RLS and incident CRDS was also examined.
Methods: Two independent, prospective cohort studies with representative, age-stratified random samples, the Dortmund Health Study (DHS; n = 1312/1122 [baseline/follow-up], median follow-up time = 2.1 years) and the Study of Health in Pomerania (SHIP; n = 4308/3300, median follow-up time = 5.0 years) were analyzed. RLS was assessed in both studies according to the RLS minimal criteria, at baseline and at follow-up. CRDS were assessed by the Center for Epidemiologic Studies-Depression scale (a score of ≥16) in DHS only at baseline and by the Munich-Composite International Diagnostic-Screener in SHIP at baseline and at follow-up.
Results: Clinically relevant depressive symptoms at baseline were associated new-onset RLS in both studies (DHS: odds ratio [OR] = 1.94, 95% confidence interval [CI] = 1.09-3.44; SHIP: OR = 2.37, 95% CI = 1.65-3.40) after adjustment for age, sex, education, body mass index, smoking, physical activity, and the presence of various comorbidities. RLS at baseline was an independent risk factor of incident CRDS in SHIP (OR = 1.82, 95% CI = 1.10-3.00).
Conclusions: The presence of CRDS may be a risk factor for subsequent RLS. The relationship between the two disorders might be bidirectional because RLS also predicts incident depressive symptoms.
Keywords: cohort study; depressive disorders; epidemiology; general population; restless legs syndrome; risk factors.