A case-control study on restless legs syndrome in nondialyzed patients with chronic renal failure

Restless legs syndrome (RLS) is a possible consequence of end-stage renal disease. However, conclusive data on the association between RLS and chronic renal failure (CRF) in nondialyzed patients are still lacking. The aims of this study were: (1) to look for an association between RLS and CRF in nondialyzed patients; (2) to analyze the characteristics of RLS and its consequences on nocturnal rest in nondialyzed patients with CRF; (3) to identify possible predictors of RLS occurrence in nondialyzed patients with CRF. We recruited 138 nondialyzed patients with CRF (mean age: 69.8 +/- 11.7 years; male: 61.6%) and 151 controls (mean age: 60.2 +/- 18.6 years; male: 42.4%). An expert in sleep medicine investigated the presence of RLS by means of a face-to-face interview. Fifteen nondialyzed CRF patients and five controls were diagnosed as RLS affected. A multivariate analysis confirmed that RLS was independently associated with CRF in nondialyzed patients (P = 0.004). CRF patients RLS(+) were more commonly women and showed the presence of an iron deficiency compared with the RLS(-) ones. Independent predictors of RLS in nondialyzed CRF patients were: female sex (OR: 10.7, 95% CI: 2.2-31.3; P = 0.004) and percentage of transferrin saturation (OR: 0.6, 95% CI: 0.4-0.9; P = 0.04). This is the first case-control study able to recognize an association between RLS and CRF in patients not yet on dialysis. Nephrologists should investigate and treat RLS in their nondialyzed patients with CRF. In particular, physicians should carefully investigate women and patients with iron deficiency in the presence of RLS symptoms.