Exposure to light at night linked to obesity, hypertension and diabetes in the elderly

In a sample of men and women aged 63 to 84, those who were exposed to any amount of light while sleeping at night were significantly more likely to be obese and to suffer from high blood pressure and diabetes compared to adults who were not exposed to any light. light at night, reports a new study from Northwestern Medicine.

Light exposure was measured with a wrist-worn device and tracked for seven days.

This is a real-world (non-experimental) study demonstrating the prevalence of any light exposure at night being linked to higher obesity, high blood pressure (called hypertension) and diabetes in older adults . It will be published on June 22 in the journal SLEEP.

Whether it’s your smartphone, leaving a TV on at night, or light pollution in a big city, we live among an abundance of artificial light sources available around the clock. Older adults are already at higher risk of diabetes and cardiovascular disease, so we wanted to see if there was a difference in the frequency of these diseases related to light exposure at night.”


Dr. Minjee Kim, corresponding author of the study, assistant professor of neurology at Northwestern University Feinberg School of Medicine and physician at Northwestern Medicine

Study investigators were surprised to find that less than half of the 552 study participants consistently had five hours of total darkness per day. The other participants were exposed to some light even during their darkest five-hour periods of the day, which were usually in the middle of their sleep at night.

Because this was a cross-sectional study, researchers don’t know if obesity, diabetes, and hypertension cause people to sleep with a light on, or if light contributed to the development of these conditions. . People with these conditions may be more likely to use the bathroom in the middle of the night (with the light on) or may have another reason for keeping the light on. A person with foot numbness due to diabetes may want to keep a night light on to reduce the risk of falling.

“It’s important for people to avoid or minimize the amount of light exposure during sleep,” said study co-lead author Dr. Phyllis Zee, chief of sleep medicine at Feinberg and physician. of Northwestern Medicine.

Zee and his colleagues are considering an intervention study to test whether restoring the natural light-dark cycle improves health outcomes such as cognition.

Zee offered tips for reducing light while sleeping:

  1. Don’t turn on the lights. If you need to have a light on (which older people may want for safety), make it a dim light closer to the ground.
  2. Color is important. Amber or red/orange light is less stimulating for the brain. Do not use white or blue light and keep it away from the sleeping person.
  3. Blackout blinds or eye masks are good if you can’t control outside light. Move your bed so outside light doesn’t shine on your face.

Who are the study participants?

Study participants were originally enrolled in the Chicago Heart Association Detection Project in Industry (CHA), a public health program and epidemiological study conducted in 1967-1973 to identify adults at high risk for heart disease on Chicago area workplaces. The study included a detailed review of known risk factors for heart disease.

Nearly 40 years later (2007-2010), Zee and Dr. Martha Daviglus, now assistant professor of preventive medicine at Feinberg, conducted a separate study (“Chicago Healthy Aging Study (CHAS)”) with 1,395 survivors of the original CHA study who agreed to participate. They underwent another detailed examination of blood pressure, weight, height, cholesterol, glucose and other known risk factors for heart disease. Additionally, they wore the actigraphy device on their non-dominant wrists for seven days and completed a daily sleep diary. Just over half of the actigraphy devices used had the ability to measure light, which forms the basis of this new study.

Other Northwestern authors include co-lead author Kathryn Reid, Thanh-Huyen Vu, Matthew Maas, Rosemary Braun, and Michael Wolf.

Source:

Journal reference:

Kim, M. et al. (2022) Nighttime light in older adults is associated with obesity, diabetes, and hypertension. Sleep. doi.org/10.1093/sleep/zsac130.

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