Association between light exposure and sleep problems related to nocturia in older adults: the Nagahama study

Abstract Background The prevalence of nocturia-related sleep problems is higher in older people. This study investigated whether morning and evening light exposure is associated with the sleep problems related to objectively identified nocturnal urination in community-dwelling older adults. Methods This cross-sectional study analyzed data collected between 2013 and 2016 for the Nagahama Prospective Cohort for Comprehensive Human Bioscience (the Nagahama Study). The study included 1585 participants aged ≥ 65 years who met the criteria for inclusion in the present analysis. An actigraph was used to measure sleep, nocturnal voiding time, and light exposure. The frequency of nocturnal voiding was derived from self-reported entries in the participants’ sleep diaries. Morning light (ML) exposure was defined as the period between waking and 12:00, while evening light (EL) exposure was defined as the period between 18:00 and bedtime. The first uninterrupted sleep period (FUSP) was calculated as the interval between the sleep onset time and the first nocturnal void. Additionally, the ratio of FUSP to sleep period time (FUSP/SPT) was calculated. Associations between light exposure parameters and the frequency of nocturnal voiding, FUSP, or FUSP/SPT were examined using multivariable linear regression models. Results Of the 1585 participants, 38.7% were male median age was 70 years. The median nocturnal voiding frequency was 1.0 times (IQR: 0.4, 1.4) and the median FUSP was 4.6 h (IQR: 3.2, 5.9). In multivariable linear regression, log ML exposure was significantly associated with FUSP and FUSP/SPT (B = 0.17, 95% CI: 0.02, 0.32; B = 2.20, 95% CI: 0.26, 4.14, respectively). In contrast, the duration of ML exposure ≥ 1,000 lx, EL exposure, and the duration of EL exposure ≥ 50 lx were not significantly associated with the frequency of nocturnal voiding, FUSP or FUSP/SPT. Conclusions Greater morning light exposure was associated with a longer FUSP. Morning bright light exposure may therefore help delay nocturia-related sleep interruptions, potentially contributing to improved sleep quality among older people.