Restless legs syndrome and mortality in kidney transplant recipients

Background: Previous studies showed an association between the presence of restless legs syndrome (RLS) and mortality in patients on dialysis therapy. An association between RLS and cardiovascular risk also was reported in the general population. However, no prospective study to date assessed the association between the presence of RLS and mortality in kidney transplant recipients. In a prospective cohort study (Transplantation and Quality of Life-Hungary Study), we tested the hypothesis that the presence of RLS predicts mortality in transplant recipients. Study Design: Prospective cohort study was performed. Settings & Participants: 804 kidney transplant recipients followed up at a single outpatient transplant center were enrolled in the study. Sociodemographic parameters, laboratory data, and medical history were collected at baseline. Data for 4-year outcomes were collected prospectively from patient charts. Predictor: Presence of RLS assessed using the RLS Questionnaire. Outcome & Measurements: We defined 3 primary outcomes: mortality with functioning graft, return to dialysis therapy, and the combined outcome of these 2. Results: Mean age was 49 +/- 13 years, estimated glomerular filtration rate was 49 +/- 19 mL/min/1.73 m(2), and median time after transplantation was 54 months. During the 4 years, 97 patients died and 63 patients returned to dialysis therapy. Mortality at 4 years was significantly greater in patients who had RLS at baseline: univariate hazard ratio for the presence of RLS was 2.53 (95% confidence interval, 1.31 to 4.87). In multivariate Cox proportional hazard analysis, the presence of RLS significantly predicted mortality (hazard ratio, 2.02; 95% confidence interval, 1.03 to 3.95) after adjustment for several covariables. Limitations: The RLS Questionnaire was not validated in transplant recipients. We lacked information for key variables, including HLA mismatch, panel reactive antibodies, cold ischemic time, acute rejection episodes, viral infections, smoking status, and dyslipidemia. Conclusions: RLS, a potentially treatable disease, is a significant risk factor for mortality in kidney transplant recipients.