Nocturia is prevalent in older adults and it vastly reduces quality of life. Yet its treatment remains inadequate because its causes are not well understood, especially nocturnal polyuria or increased urine production at night. This study, which builds on the investigators' ongoing research, would be the first of its kind to explore the role of sleep in nighttime urine production. The findings will contribute important knowledge to guide development of better targeted and more effective therapy for this prevalent and morbid condition.