Independent Associations Between Nocturia and Nighttime Blood Pressure/Dipping in Elderly Individuals: The HEIJO-KYO Cohort

Abstract

Objectives: To evaluate the association between nocturnal void frequency and ambulatory blood pressure (BP).

Design: Cross-sectional.

Setting: Nara, Japan.

Participants: Community-based elderly individuals (mean age 72.1, N = 867).

Measurements: Nocturnal void frequency and ambulatory BP.

Results: Two hundred twenty-four participants had no nocturnal void, 384 had one nocturnal void, and 259 had two or more nocturnal voids. Univariate comparisons showed that more-frequent nocturnal voiding was significantly associated with higher nighttime systolic BP (SBP) and lower dipping (nocturnal voids: ≥2, nighttime SBP 121.1 mmHg, dipping 11.8% vs 0, nighttime SBP 111.5 mmHg, dipping 15.8%, P < .001). Multivariate models revealed that two or more nocturnal voids was significantly associated with higher nighttime SBP and lower dipping than no nocturnal voids (adjusted mean difference for nighttime SBP (nocturnal voids ≥2 minus 0): 6.3 mmHg, 95% confidence interval (CI) = 2.6 to 10.1 mmHg, P < .001; adjusted mean difference for dipping (nocturnal voids ≥2 minus 0): -2.8%, 95% CI = -4.9% to -0.7%, P = .005) and that the associations were independent of potential confounding factors such as age, sex, body mass index, smoking status, antihypertensive use, diabetes mellitus, renal function, asymmetric dimethylarginine, bedtime, length of time in bed, daytime and nighttime physical activity, endogenous melatonin levels, and bedroom light levels. In contrast, one void per night was not significantly associated with nighttime SBP and dipping.

Conclusion: Nocturia is significantly associated with nighttime SBP and dipping in the general elderly population, independent of several confounding factors such as age, sex, metabolic abnormalities, physical activity, and circadian rhythm parameters.

Keywords: circadian rhythm; dipping; nighttime blood pressure; nocturia; physical activity.