Loss of normal circadian profile of urine excretion in idiopathic restless legs syndrome

Background This study was performed to elucidate preliminary observations of excessive nighttime urine excretion in idiopathic restless legs syndrome (iRLS). Methods Seventeen patients, with normal serum creatinine, blood urea nitrogen, and urate, and 11 healthy controls were examined. We measured excretory renal function parameters (urine volume, osmolarity, sodium, chloride, potassium, calcium, phosphate, microalbumin, aldosterone, creatinine) between 7:00 am and 10:00 pm and between 10:00 pm and 7:00 am. Results During the nighttime, volume ( P =0.006), sodium ( P =0.009), and chloride excretion ( P =0.001) were significantly higher, and osmolarity ( P =0.025) was significantly lower in patients as compared to controls. In comparing daytime to nighttime, controls showed the physiological reduced nocturnal excretion of volume ( P =0.009) and chloride ( P =0.023), and an increased osmolarity ( P =0.026), but patients showed similar excretion rates of these parameters (all differences ns). Conclusions These data indicate a loss of normal circadian profile of urine excretion in iRLS. The elevated nighttime excretion, with values similar to those in the daytime, hint at a possibly elevated fluid, sodium, and chloride intake during daytime.