Indoor cold exposure and nocturia: a cross-sectional analysis of the HEIJO-KYO study

Objectives To investigate the association between indoor cold exposure and the prevalence of nocturia in an elderly population. Subjects and Methods The temperature in the living rooms and bedrooms of 1 065 home-dwelling elderly volunteers (aged >= 60 years) was measured for 48 h. Nocturia (>= 2 voids per night) and nocturnal urine production were determined using a urination diary and nocturnal urine collection, respectively. Results The mean +/- SD age of participants was 71.9 +/- 7.1 years, and the prevalence of nocturia was 30.8%. A 1 degrees C decrease in daytime indoor temperature was associated with a higher odds ratio (OR) for nocturia (1.075, 95% confidence interval [CI] 1.026-1.126; P = 0.002), independently of outdoor temperature and other potential confounders such as basic characteristics (age, gender, body mass index, alcohol intake, smoking), comorbidities (diabetes, renal dysfunction), medications (calcium channel blocker, diuretics, sleeping pills), socio-economic status (education, household income), night-time dipping of ambulatory blood pressure, daytime physical activity, objectively measured sleep efficiency, and urinary 6-sulphatoxymelatonin excretion. The association remained significant after adjustment for nocturnal urine production rate (OR 1.095 [95% CI 1.042-1.150]; P < 0.001). Conclusions Indoor cold exposure during the daytime was independently associated with nocturia among elderly participants. The explanation for this association may be cold-induced detrusor overactivity. The prevalence of nocturia could be reduced by modification of the indoor thermal environment.