It’s not just artificial food that could impact your risk of Alzheimer’s disease. A recent study published in Frontiers of Neuroscience found an increased risk of this incurable mental illness associated with living in areas full of artificial outdoor light at night.

According to Medicare claims and analysis of light pollution in states and counties, areas with higher average nighttime light intensity experienced increased rates of Alzheimer’s disease.

The prevalence of Alzheimer’s disease among adults aged 65 or older was more strongly linked with nightly light pollution exposure compared to alcohol intake, chronic kidney disease, depression, or obesity.

Greater nighttime light intensity had a stronger link to Alzheimer’s disease risk in individuals younger than 65 than any other risk factors examined in the study.

Robin Voigt-Zuwala, PhD, lead author and director, Circadian Rhythm Research Laboratory, Rush University, Chicago, Illinois notes, “The results are pretty striking when you do these comparisons and it’s true for people of all ages.”

Shedding Some Light

Several negative consequences occur due to exposure to artificial outdoor light at night, including disruption in sleep, atherosclerosis, cancer, and obesity. This is the first study to examine the risk for Alzheimer’s disease, according to the researchers.

Higher risks for mild cognitive impairment were found in Chinese veterans and late-onset dementia in Italian residents in areas with brighter light at night in two recent studies.

The connection between Alzheimer’s disease prevalence and average nighttime light intensity in the lower 48 states utilizing data from the Centers for Disease Control and Prevention, Medicare Part A and B, and NASA satellite–acquired radiance data were evaluated by Dr. Voigt-Zuwala and colleagues for this study.

Data was averaged between 2012-2018 and states were divided into five groups based on average nighttime light intensity.

The darkest states were Montana, Wyoming, South Dakota, Idaho, Maine, New Mexico, Vermont, Oregon, Utah, and Nevada. The brightest states were Indiana, Illinois, Florida, Ohio, Massachusetts, Connecticut, Maryland, Delaware, Rhode Island, and New Jersey.

A significant difference in risk of Alzheimer’s disease between state groups was noted using analysis of variance. States with the lowest average nighttime light had lower rates of Alzheimer’s disease compared to those with higher intensity, according to multiple comparisons testing.

Utilizing data from 45 counties and the District of Columbia, the same positive relationship was seen when each year was evaluated individually and at the county level.

Strong Link

The state average nighttime light intensity is significantly associated with Alzheimer’s disease prevalence, the investigators observed. This impact was noted across all ages, sexes, and races except Asian Pacific Island, the authors noted, the latter possibly associated with statistical power.

When known or proposed risk factors for Alzheimer’s disease such as atrial fibrillation, diabetes, hyperlipidemia, hypertension, and stroke were included in the model, a stronger connection with Alzheimer’s disease than average nighttime light intensity was observed.

However, nighttime light intensity was more strongly associated with Alzheimer’s disease prevalence than alcohol abuse, chronic kidney disease, depression, heart failure, and obesity.

In addition, in people younger than 65 years, nighttime light pollution had a stronger association with Alzheimer’s disease prevalence than any other risk factors.

It’s unknown what the mechanism behind this increased risk is, but it may be related to genetic susceptibility of an individual and how they respond to light, suggested Dr. Voigt-Zuwala.

She noted that “APOE4 is the genotype most highly associated with Alzheimer’s disease risk, and maybe the people who have that genotype are just more sensitive to the effects of light exposure at night, more sensitive to circadian rhythm disruption.”

The authors noted that more studies are needed but suggested light pollution may also impact Alzheimer’s disease through sleep disturbance, which can increase inflammation, activate microglia and astrocytes, and disrupt the clearance of amyloid beta by reducing levels of brain-derived neurotrophic factors.

If you’re not living in the “darkest states,” you can still reduce your risk for Alzheimer’s disease. Below are some suggestions for more sound sleep:

·         Keep a consistent sleep schedule. Go to bed at roughly the same time and get up the same time each day. This includes weekends.

·         Do regular exercise to tire yourself out.

·         Make sleep a priority. Turn off all screens (cell phones, computers, tablets, and TVs) at least three hours before bed.

·         Invest in blackout curtains to reduce outside light.

·         Avoid caffeine after 2 PM to prevent insomnia or other sleep disruption.

·         Skip the late-night snacks which may affect sleep and risk for reflux.

·         Avoid alcohol close to bedtime. It may help you fall asleep, but increases the risk of waking as well as hot flashes.

·         Wear loose-fitting comfortable clothes to bed.

·         Don’t read the news or emails right before bed.

·         Sleep in separate rooms if your partner snores.

Lisa Andrews, MEd, RD, LD

References

1.       Voigt, et. al. Outdoor nighttime light exposure (light pollution) is associated with Alzheimer’s diseaseFront. Neurosci., 05 September 2024 Volume 18 - 2024 | https://doi.org/10.3389/fnins.2024.1378498

2.       Yan Chen, et. al. Long-term exposure to outdoor light at night and mild cognitive impairment: A nationwide study in Chinese veterans, Science of The Total Environment, Volume 847, 2022 157441, ISSN 0048-9697, https://doi.org/10.1016/j.scitotenv.2022.157441.

3.       Mazzoleni, Elena et al. Outdoor artificial light at night and risk of early-onset dementia: A case-control study in the Modena population, Northern Italy. Heliyon, Volume 9, Issue 7, e17837