Keeping Any Light on While Sleeping Is Linked to Obesity, Diabetes, and High Blood Pressure
By NORTHWESTERN UNIVERSITY
Night lights, left-on
TVs, and smartphones have all been related to dramatically greater disease
rates
A recent Northwestern Medicine study of older men and
women aged 63 to 84 found that individuals who were exposed to any level of
light while sleeping at night were considerably more likely to be obese, have
high blood pressure, and have diabetes than people who were not exposed to any light
at all.
Over the course of seven days, light exposure
was assessed using a wrist-worn device.
The prevalence of any nighttime light exposure
being connected to greater rates of obesity, high blood pressure (also known as
hypertension), and diabetes in older adults can be seen in this real-world (not
experimental) study. On June 22nd, 2022, the research was published in the
journal SLEEP.
“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 amount of artificial sources of light that are available 24 hours of a day,” said study corresponding author Dr. Minjee Kim, assistant professor of neurology at Northwestern University Feinberg School of Medicine and a Northwestern Medicine physician.
“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.”
Less than half of the 552 study participants regularly
saw a five-hour period of total darkness each day, which astonished the study’s
researchers. Even during their five darkest hours of the day, which were often
in the middle of sleep at night, the rest of the participants were exposed to
some light.
Researchers are unsure of whether obesity,
diabetes, and hypertension cause individuals to sleep with a light on or
whether the light contributes to the development of these disorders since this
was a cross-sectional study. With the light on, people with these conditions
may be more prone to use the restroom in the middle of the night or have other
reasons. A night light may be left on by a diabetic who has foot numbness to
lessen the chance of falling.
“It’s important for people to avoid or minimize
the amount of light exposure during sleep,” said senior study co-author Dr.
Phyllis Zee, chief of sleep medicine at Feinberg and a Northwestern Medicine
physician.
Zee and colleagues are considering an
intervention study to test whether restoration of the natural light-dark cycle
improves health outcomes such as cognition.
Zee offered tips to reduce light during sleep:
- Don’t
turn the lights on. If you need to have a light on (which older adults may
want for safety), make it a dim light that is closer to the floor.
- Color
is important. Amber or red/orange light is less stimulating for the brain.
Don’t use white or blue light and keep it far away from the sleeping
person.
- Blackout
shades or eye masks are good if you can’t control the outdoor light. Move
your bed so the outdoor light isn’t shining on your face
Who are the study
participants?
The study participants were originally enrolled
in the Chicago Heart Association Detection Project in Industry (CHA), a public
health program and an epidemiologic study conducted from 1967-1973 to identify
high-risk adults for heart diseases in workplaces throughout the Chicago area.
The study included a detailed examination of known risk factors for heart
disease.
Almost 40 years later (2007-2010), Zee and Dr. Martha Daviglus, now an adjunct 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. In addition, they wore
the actigraphy device on their non-dominant wrists for seven days and filled
out a daily sleep diary. Slightly more than half of the actigraphy devices used
had the capacity to measure light, which constitutes the basis of this new
study.
The study was funded by the National Heart,
Lung, and Blood Institute (grants R01 HL089695, R01 HL090873, R01 HL021010),
the National Center for Advancing Translational Sciences (UL1TR001422), and the
National Institute on Aging (P30AG059988), all of the National Institutes of Health.
Reference: “Light at night in older age is
associated with obesity, diabetes, and hypertension” by Minjee Kim, Thanh-Huyen
Vu, Matthew B Maas, Rosemary I Braun, Michael S Wolf, Till Roenneberg, Martha L
Daviglus, Kathryn J Reid and Phyllis C Zee, 22 June 2022, SLEEP.
DOI:
10.1093/sleep/zsac130