| Abstract: | Circadian misalignment between internal and environmental rhythms dysregulates blood pressure (BP) variability because of disruption of the biological clock, resulting in increased nighttime BP. Although exposure to light-at-night is associated with the circadian misalignment, it remains unclear whether exposure to light-at-night in home settings is associated with nighttime BP. In this cross-sectional analysis of 528 elderly individuals (mean age: 72.8 years), we measured bedroom light intensity at 1-min intervals on two consecutive nights along with ambulatory BP, overnight urinary melatonin excretion and actigraphy. With regard to adjusted mean comparisons using analysis of covariance, the light-at-night group (average: ≥5?lux; n?=?109) showed significantly higher nighttime systolic BP (SBP; adjusted mean: 120.8 vs. 116.5?mmHg, p?=?0.01) and diastolic BP (70.1 vs. 67.1?mmHg, p?<?0.01) compared with the Darker group (average: <5?lux; n?=?419) independently of potential confounding factors including overnight urinary melatonin excretion and actigraphic sleep quality. We observed consistent associations between light-at-night and nighttime BP in different cutoff values for light-at-night intensity (i.e. 3 and 10?lux). In conclusion, exposure to light-at-night in home settings is significantly associated with increased nighttime BP in elderly individuals independently of overnight urinary melatonin excretion. A 4.3?mmHg increase in nighttime SBP is associated with a 6.1% increase in total mortality, which corresponds to approximately 10?000 annual excess deaths in Japanese elderly population. |
