Association between before-bedtime passive body heating and nocturia during the cold season among older adults.

Background Cold exposure induces lower urinary tract symptoms including nocturia. Cold-induced detrusor overactivity can be alleviated by increasing skin temperature in rats. However, no study has shown an association between passive heating with hot-water bathing and nocturia among humans.Methods We included 1,051 Japanese community-dwelling older adults (mean age 71.7 years) in this cross-sectional study from 2010 to 2014. The number of nocturnal voids was recorded in a self-administered urination diary. Nocturia was defined as ≥2 nocturnal voids. We evaluated bathing conditions in the participants' houses.Results Hot-water bathing (n = 888) was associated with a lower prevalence of nocturia than no bathing (n = 163), independent of potential confounders including age, sex, obesity, income, physical activity, diabetes, medication (diuretics, nondiuretic antihypertensives, and hypnotics), depressive symptoms, indoor/outdoor temperature, and day length (odds ratio [OR]: 0.68, 95% confidence interval [CI]: 0.48-0.97; p = 0.035). Compared with the quartile group with the longest bath-to-bed interval (range: 161-576 min), the second and third quartile groups (range: 61-100 and 101-160 min, respectively) were associated with a lower prevalence of nocturia, after adjusting for water temperature and bathing duration besides the same covariates (OR: 0.60, 95% CI: 0.38-0.96; p = 0.031 and OR: 0.59, 95% CI: 0.37-0.94; p = 0.025, respectively).Conclusion Hot-water bathing, particularly with a bath-to-bed interval of 61-160 min, was significantly associated with a lower prevalence of nocturia among older adults.