Older people exposed to light during their sleep at night were more likely to have conditions including diabetes and high blood pressure, research has found.

A group of 552 women and men aged from 63 to 84 years wore a device to measure light exposure as they slept, over a period of seven days.

The research team from Northwestern University in America found that less than half of the participants slept in complete darkness on a regular basis.

The team has said that more research needs to be carried to determine whether having conditions such as obesity, diabetes or high blood pressure means people sleep with a light on, or if light exposure can lead to these conditions. Having to use the toilet during the night, for example, could mean people tend to leave a light on, or to reduce the risk of falls.

Dr Minjee Kim, assistant professor of neurology at Northwestern University Feinberg School of Medicine, said: “Whether it be from one’s smartphone, leaving a TV on overnight or light pollution in a big city, we live among an abundant number of artificial sources of light that are available 24 hours of a day.

“Older adults already are at higher risk for diabetes and cardiovascular disease, so we wanted to see if there was a difference in frequencies of these diseases related to light exposure at night.”

The team is now looking to carry out a further study to see whether reducing light exposure during sleep brings about health improvements.

Their top tips for reducing light exposure at night include:

  • If you need to have a light on, ensure it is a dim one that is close to the floor
  • Avoid white or blue light – opt for amber, red or orange lighting, which does not stimulate the brain as much
  • Use eye masks or blackout blinds if you can’t avoid outdoor light getting in, and move your bed to a position where it’s exposed to the least amount of light.

Study co-author Dr Phyllis Zee, chief of sleep medicine at Feinberg, added: “It’s important for people to avoid or minimise the amount of light exposure during sleep.”

The study has been published in the journal Sleep.

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