Study: Light During Sleep in Older Adults Is Linked to Diabetes, High Blood Pressure, Obesity


Study results show that there is a link between leaving the television on, night lights, and smart phones and higher disease rates.

Individuals aged 63 to 84 years who were exposed to any amount of light while sleeping at night were significantly more likely to be obese, have diabetes, and have high blood pressure compared with adults who were not exposed to any light during the night, according to data from a Northwestern Medicine study.

In the real-world study that was published in Sleep, investigators used wrist-worn devices to measure and track light exposure over 7 days.

“Whether it be from one’s smart phone, leaving a TV on overnight, or light pollution in a big city, we live among an abundant number amount of artificial sources of light that are available 24 hours of a day,” Minjee Kim, MD, assistant professor of neurology at Northwestern University Feinberg School of Medicine and physician at Northwestern Medicine, said in a statement.“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 study results showed that less than half the 552 individuals in the study consistently had a 5-hour period of complete darkness per day. The rest of the individuals were exposed to some light, even during their darkest 5-hour periods of the day, which were usually in the middle of their sleep.

Because of the nature of the study, investigators did not know if diabetes, hypertension, and obese cause individuals to sleep with the light on or if the light contributed to the development of these conditions.

Individuals with the former conditions may be more likely to use the bathroom with the light on in the middle of the night or may have another reason to keep the light on. For example, an individual with foot numbness related to diabetes might leave the light on to reduce the risk of falling.

Investigators are considering an intervention study to test whether a restoration of natural light-dark cycles improves health outcomes including cognition.

“It’s important for people to avoid or minimize the amount of light exposure during sleep,” Phyllis Zee, MD, PhD, chief of sleep medicine at Feinberg and a Northwestern Medicine physician, said in the statement.

The investigators offered tips to reduce light during sleep, including keeping the lights off or having a dim light on closer to the floor; using amber or red/orange light instead of blue or white light when sleeping; and using blackout curtains or eye masks if needed to reduce the amount of light.

The individuals in the study were enrolled in the Chicago Heart Association Detection project in Industry, a public health program and epidemiologic study conducted to identify individuals at high risk for heart disease in workplaces throughout the Chicago, Illinois, area.

In addition, investigators included a detailed examination of known risk factors for heart disease.


Light during sleep in older adults linked to obesity, diabetes, high blood pressure. EurekAlert. News release. June 22, 2022. Accessed June 30, 2022.

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