Outdoor light at night may be a major risk factor for Alzheimer’s disease, according to new research from Rush.
While light pollution is associated with an increased risk of some disorders and diseases, this is the first time it has been linked to Alzheimer’s disease.
The study was conducted at Rush University Health System and published in Frontiers in neuroscience.
“Our research shows that there is an association in the U.S. between Alzheimer’s disease prevalence and nighttime light exposure, particularly in people younger than 65 years,” said lead researcher Robin Voigt-Zuwala, PhD, an associate professor at Rush. “Nighttime light pollution, a modifiable environmental factor, may influence Alzheimer’s risk.”
High light levels in the US
While legislation in some states aims to reduce light pollution, nighttime light levels remain high in many parts of the country.
By studying light pollution maps, the researchers looked at all 48 contiguous states and incorporated medical data associated with Alzheimer’s risk factors and divided groups by light intensity. Across all five groups, they found that light intensity was correlated with Alzheimer’s prevalence, even when some well-established disease factors were not.
Although the cause is unknown, higher nighttime light intensity was associated with a higher prevalence of Alzheimer’s disease than any other risk factor examined in the study for those under age 65, suggesting that younger people may be more sensitive to the effects of light exposure at night.
“Certain genes may influence the early onset of Alzheimer’s disease, and these same genes may lead to increased vulnerability to the effects of nighttime light exposure,” Voigt-Zuwala explained. “Moreover, younger people are more likely to live in urban areas and have lifestyles that may increase nighttime light exposure.”
Reduce exposure to light
Light exposure influences the body’s natural sleep-wake pattern, which is called the circadian rhythm. Light exposure at night can disrupt a person’s circadian rhythm, which can promote inflammation and make a person less resilient and more prone to disease. The researchers did not examine light inside the home at night or how it might affect health.
Voigt-Zuwala said: “The good news is that simple changes can be made with minimal effort to reduce light exposure at night, by adding blackout curtains or sleeping with an eye mask.”
The research results are limited to a subset of the population and more evidence is needed to better understand the connection between outdoor light at night and Alzheimer’s disease.