Bright nights and dark days can lead to an early grave

Researchers examined whether personal daylight, nighttime lighting, and lighting patterns that disrupt our circadian rhythms impact mortality risk.

Published in the magazine Proceedings of the National Academy of Sciences, The results show that those exposed to bright light at night had a 21-34% increased risk of death, while those exposed to bright daylight had a 17-34% reduced risk of death.

“Exposure to brighter nights and darker days can disrupt our circadian rhythms, a disruption that is known to lead to a variety of health problems including diabetes, obesity, cardiovascular disease, mental health problems and increases the risk of death,” says senior author and sleep expert. Professor Sean Kane from Flinders University.

“This new evidence about the potential harmful effects of light shows us how important individual light exposure is to your health.”

Co-senior author Associate Professor Andrew Phillips says exposure to light at night disrupts circadian rhythms by shifting the timing (phase shift) and weakening the signal (amplitude suppression) of the central circadian “pacemaker,” which controls circadian rhythms throughout the body.

“Disruption of the body’s circadian rhythm is associated with the development of metabolic syndrome, diabetes and obesity, and is also directly associated with the development of cardiometabolic diseases, including myocardial infarction, stroke and hypertension,” says Associate Professor Phillips.

“The observed association of night light exposure with mortality risk may be explained by the fact that night light disrupts circadian rhythms, leading to adverse cardiometabolic consequences.

“Our findings clearly show that avoiding night light and seeking daylight can promote optimal health and longevity, and this recommendation is simple, accessible and cost-effective,” adds Associate Professor Phillips.

Study authors from FHMRI Sleep Health examined the association of personal light exposure with the risk of all-cause and cardiometabolic mortality in 89,000 UK Biobank participants aged 40 to 69 years. Measurements were recorded using wrist-worn sensors, and participant mortality was recorded by the National Health Service over a follow-up period of approximately 8 years.

Sleep duration, sleep efficiency, and sleep midpoint were assessed from movement data, and cardiometabolic mortality was defined as any cause of death consistent with circulatory, endocrine, and metabolic diseases.

The study also found that circadian rhythm disruption predicted a higher risk of mortality, which the authors were able to determine using computer modeling. Results took into account age, sex, ethnicity, photoperiod, and sociodemographic and lifestyle factors.

Lead author Dr Daniel Windred says the findings demonstrate the importance of maintaining a dark environment during the night and early morning hours, when the central circadian “pacemaker” is most sensitive to light, and seeking out bright light during the day to improve our performance. circadian rhythms.

“Protecting lighting conditions may be especially important for those at risk for both circadian disruption and mortality, such as those in intensive care units or aged care,” says Dr. Windred.

“In the general population, avoiding night light and seeking daylight may lead to reduced morbidity, especially cardiometabolic disease, and increased life expectancy.”