Impact of Nocturia on Mortality: The Nagahama Study

Abstract

Purpose: Nocturia has been reported as a risk factor for mortality. However, evidence is limited and has a high risk of bias. We evaluated the association between nocturia and mortality using longitudinal data from the general Japanese population.

Materials and methods: Data were obtained from the Nagahama Cohort Project, a longitudinal, general population cohort study. Nocturia was measured using the International Prostate Symptom Score. Mortality data were obtained from the Basic Resident Register in Nagahama City. We used Cox proportional hazard models and time-varying covariates at baseline and 5-year followup to analyze the association between nocturia and mortality.

Results: We analyzed 9,762 participants (median age 56.8 years, male 32.8%). The prevalence rates of nocturnal voiding at 0, 1, 2 and 3 or more times were 44.3%, 39.1%, 11.7% and 4.9%, respectively. A total of 263 participants died. Followup assessment was performed 3,224 (SD 537) days after baseline. According to multivariable Cox proportional hazard regressions, mortality increased dose dependently with the nocturnal voiding frequency as HR 1.46 for 1 time (95% CI 1.02-2.09), HR 1.85 for 2 times (95% CI 1.23-2.77) and HR 2.06 (95% CI 1.28-3.32) for 3 or more times in comparison with 0 times (p for trend=0.00084). In the time varying Cox proportional hazard regression the association was still significant (p for trend=0.0017).

Conclusions: According to this longitudinal study with a low incidence of missing data and high representation of the general population, nocturia is associated with mortality.

Keywords: cohort studies; longitudinal studies; mortality; nocturia.