People who regularly experience lighter nights and darker days are at higher risk of mortality, research suggests

A team of biologists, medical researchers and sleep specialists from various institutions in Australia, the US and the UK have found that people who regularly experience lighter nights and/or darker days tend to have a higher mortality risk.

In their studies published in the Proceedings of the National Academy of Sciences, the group analyzed patient data in the UK Biobank, focusing on sleep patterns and lighting.

Previous research has shown that frequent interruptions to the circadian rhythm can lead to a host of health problems, including an increase in premature death.

In this new effort, the research team wondered about the impact of light on the circadian cycles of people who are regularly awake at night, and by extension, their risk of dying prematurely. To find out, they accessed and analyzed data from the UK Biobank, a repository of biomedical data for hundreds of thousands of people in Britain.

The researchers looked for records of people wearing wrist devices that tracked light exposure and found 89,000 in the database. After filtering, the test cases were narrowed down to 88,905 people, most of whom were white and over 62 years old.

The researchers focused on the mortality of those followed over an eight-year period, and their exposure to light at night or darkness during the day.

They found 3,750 deaths in the sample, of which 798 were related to heart problems. They also found a link between light exposure at night and an increased risk of premature death. The increased risk appeared to be most pronounced for people with heart disease.

The researchers also found that people who were regularly exposed to more light than average during the day reduced their mortality risk. The researchers were also able to see disruptions to the circadian rhythm in people who regularly experience light at night, putting them at risk for a wide range of conditions.

The research team suggests that people stay dark late at night and early in the morning, when the circadian rhythm is most susceptible to disruption. And if possible, they should expose themselves to more light during the day.

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