Atrial natriuretic peptide levels in geriatric patients with nocturia and nursing home residents with nighttime incontinence

OBJECTIVES: To determine if nocturnal polyuria in geriatric patients with nocturia and nocturnal incontinence is associated with elevated plasma atrial natriuretic peptide (ANP) levels. DESIGN: Case series. SETTING: Four nursing homes and two board and care facilities. PARTICIPANTS: Fifty-four nursing home residents and 26 board and care residents with a mean age of 86. MEASUREMENTS: Daytime (7:00 a.m. to 7:00 p.m.) and nighttime (7:00 p.m. to 7:00 a.m.) urine volumes of incontinent nursing home residents were measured over 3 days and 3 nights by reweighing preweighed adults diapers and toileting inserts emptied by research staff for the board and care group. Blood was drawn in the early morning (5:00 a.m. to 7:00 a.m.) before subjects arose and in the evening after an hour of lying in bed (8:00 p.m. to 11:00 p.m.), and plasma ANP levels were determined by radioimmunoassay. RESULTS: Forty-nine (61%) of the subjects had nocturnal polyuria as defined by night/total urine volume ratios ≥ 50%. There was no significant difference between those with night/total ratios ≥ 50% versus <50% in plasma levels of ANP in the early morning (44.2 ± 33.3, median 35.7 pg/mL vs 40.9 ± 39.2, median 28.5; P = .36 by Mann Whimey U) or in the evening (43.4 ± 28.8, median 36.4 pg/mL vs 49.6 ± 53.1, median 34.4; P = .58). Nor was there any significant correlation between night/total urine volume ratio and morning or evening ANP levels (r = .01, P = .96 and r = .23, P = .31, respectively). CONCLUSIONS: In this sample of geriatric patients with nocturia and nursing home residents with nighttime urinary incontinence, ANP levels were elevated, but increased nighttime urine production was not associated with higher levels. Because of the variability in ANP levels, our power to detect such an association was low, and we cannot draw any definitive conclusions. Although high plasma ANP levels are unlikely to be a primary cause of nocturia and nighttime incontinence, they may, when combined with other factors such as low antidiuretic hormone levels, sleep disorders, and low functional bladder capacity, contribute to these symptoms in some geriatric patients.