By John Salak –
Living long or dying early may be a matter of light nights and dark days. The warning from researchers is based on more than 13 million hours of data, collected from light sensors worn by almost 90,000 people. They found exposure to bright nights and dark days is associated with an increased risk of death. Light nights is a grave matter—our bodies are finely tuned to natural rhythms and disrupting these cycles can have serious consequences.
The study by Flinders University focused on whether personal day and night light, in effect lighting patterns that disrupt our circadian rhythms, predicted mortality risk. The results show that those who were exposed to high levels of light at night had a 21-34 percent increased risk of death, while those exposed to high levels of daylight had a 17-34 percent reduction in their risk of death.
“Exposure to brighter nights and darker days can disrupt our circadian rhythms, a disruption that is known to lead to various health issues including diabetes, obesity, cardiovascular disease, mental health issues and increase the risk of death,” says senior author and sleep expert Professor Sean Cain. “These new insights into the potential adverse impact of light have shown us just how important personal light exposure patterns are for your health.”
Light exposure at night disrupts circadian rhythms by shifting the timing and weakening the signal of the central circadian ‘pacemaker’ which orchestrates circadian rhythms throughout the body, explained Associate Professor Andrew Phillips, the study’s co-senior author.
“Disruption to the body’s circadian rhythms is linked to the development of metabolic syndrome, diabetes and obesity and is also strongly implicated in the development of cardiometabolic diseases including myocardial infarction, stroke and hypertension,” Phillips added. “The observed relationships of night light exposure with mortality risk may be explained by night light disrupting circadian rhythms, leading to adverse cardiometabolic outcomes.”
The study underscored the importance of monitoring light exposure. “Our findings clearly show that avoiding night light and seeking daylight may promote optimal health and longevity, and this recommendation is easy, accessible and cost-effective,” Phillips noted.
The metrics recorded by the research team came from wrist worn sensors. The participant mortality rates were captured by the National Health Service across a follow-up period of approximately 8 years. Sleep duration, sleep efficiency and midsleep were estimated from motion data, while cardiometabolic mortality was defined as any cause of death corresponding to diseases of the circulatory system, or endocrine and metabolic diseases.
The research showed a disrupted circadian rhythm predicted higher mortality risk, which the authors were able to determine using computer modelling.
The findings demonstrate the importance of maintaining a dark environment across the late night and early morning hours when the central circadian ‘pacemaker’ is most sensitive to light. In contrast, seeking bright light during the day to enhance our circadian rhythms, lead author Dr. Daniel Windred noted.
“Protection of lighting environments may be especially important in those at risk for both circadian disruption and mortality, such as in intensive care or aged-care settings,” he added. “Across the general population, avoiding night light and seeking day light may lead to reduction in disease burden, especially cardiometabolic diseases and may increase longevity.”
