Impact of Sleep on Chronobiology of Micturition among Healthy Older Adults.

Nocturia (waking to void) is prevalent among older adults. Disruption of the well-described circadian rhythm in urine production with higher nighttime urine output is its most common cause. In young adults, their circadian rhythm is modulated by the 24-hour secretory pattern of hormones that regulate salt and water excretion; including antidiuretic hormone (ADH), renin, angiotensin, aldosterone, and atrial natriuretic peptide (ANP). The pattern of hormone secretion is less clear in older adults. We investigated the effect of sleep on the 24-hour secretion of these hormones in healthy older adults. Thirteen participants aged ≥65 years underwent two 24-hour studies at a Clinical Research Center, 6 weeks apart. The first used a habitual wake-sleep protocol and the second used a constant routine protocol that removed the influence of sleep, posture, and diet. To assess hormonal rhythms, plasma was collected at 8am, 12pm, 4pm, and every 30 minutes 7pm-7am. Mixed-effects regression model was used to compare subject-specific and mean trajectories of hormone secretion under the two conditions. ADH, aldosterone, and ANP showed a diurnal rhythm that peaked during sleep in the wake-sleep protocol. These nighttime elevations were significantly attenuated within subjects during the constant routine. We conclude that sleep has a masking effect on circadian rhythm amplitude of ADH, aldosterone, and ANP: the amplitude of each is increased in the presence of sleep and reduced in the absence of sleep. Disrupted sleep could potentially alter nighttime urine output in healthy older adults via this mechanism.