Exposure to excessive light pollution linked to Alzheimer’s disease

Streetlights, illuminated signs, and roadway lighting help reduce crime, improve road safety, and enhance urban aesthetics. While lighting at night has its benefits, constant exposure to artificial light also brings unintended consequences, including ecological disruptions and potential health risks.

Light pollution, particularly, is emerging as a potential risk factor for various conditions, and recent research has explored its connection to Alzheimer's disease (AD).

In the U.S., some states have enacted legislation aimed at reducing light pollution, yet nighttime light levels remain elevated in many regions. A new study from researchers at Rush University Medical Center delves into the association between outdoor light pollution at night and the prevalence of Alzheimer's disease.

The study, published in Frontiers in Neuroscience, uncovers concerning findings about the relationship between light exposure and AD risk, particularly in individuals under 65.

“We show that in the U.S., there is a positive association between AD prevalence and exposure to light at night, particularly in those under the age of 65,” explains Dr. Robin Voigt-Zuwala, the study's first author and an associate professor at Rush University Medical Center. “Nightly light pollution – a modifiable environmental factor – may be an important risk factor for AD.”

To conduct the study, researchers analyzed light pollution data from across the lower 48 states, combining this information with medical records detailing common risk factors for Alzheimer's disease. They categorized the intensity of nighttime light into five groups, ranging from the lowest to the highest levels of light pollution.

The findings were striking: light pollution appears to play a significant role in the prevalence of Alzheimer's, especially in people younger than 65.

In older adults (65+), the study revealed that the correlation between light pollution and Alzheimer's was stronger than for some well-established risk factors, such as alcohol abuse, chronic kidney disease, depression, and obesity. However, other factors like diabetes, high blood pressure, and stroke showed even stronger links to Alzheimer's than light pollution.

In contrast, for individuals younger than 65, higher exposure to nighttime light was associated with a greater prevalence of Alzheimer's than any other risk factor examined. This result suggests that younger people may be especially vulnerable to the effects of light pollution.

The researchers speculate that this increased vulnerability could stem from various factors, including differences in light sensitivity. "Certain genotypes, which influence early-onset AD, impact the response to biological stressors, which could account for increased vulnerability to the effects of nighttime light exposure,” Voigt-Zuwala notes.

Additionally, younger individuals often live in more urbanized environments where light pollution is more intense, potentially increasing their exposure to artificial light.

The reasons behind the higher risk for younger adults aren't yet fully understood, but one possible explanation involves how genetics interact with environmental factors. Certain genes associated with early-onset Alzheimer's may affect how the body responds to stressors like light pollution, potentially making some individuals more susceptible.

Urban living, common among younger populations, may further amplify the risk. Those in cities tend to have more exposure to artificial light due to lifestyle factors like longer working hours, nightlife, and proximity to light-emitting infrastructure.

These findings suggest that for younger people, lifestyle and environment may play a critical role in how light exposure impacts their health. While the study didn’t directly investigate the impacts of indoor lighting, it's well-known that exposure to blue light from screens and other devices can disrupt sleep and circadian rhythms, both of which are important in maintaining cognitive function.

Therefore, reducing overall light exposure, both indoors and outdoors, could be a key preventive measure for those at higher risk for Alzheimer's.

While the study indicates that light pollution is a significant environmental factor linked to Alzheimer's disease, it also highlights that the problem is modifiable. Raising awareness about this connection could help people make changes to protect their cognitive health. Voigt-Zuwala suggests that simple steps, like installing blackout curtains or using sleep masks, can reduce the amount of light you're exposed to while sleeping.

“Awareness of the association should empower people – particularly those with risk factors for AD – to make easy lifestyle changes,” says Voigt-Zuwala. “Easy-to-implement changes include using blackout curtains or sleeping with eye masks. This is useful especially for those living in areas with high light pollution.”

But outdoor light pollution isn't the only concern. The type of light you're exposed to inside your home matters, too. While this study focused on outdoor lighting, previous research has shown that blue light from electronic devices has the greatest impact on sleep disruption. To minimize indoor light pollution, you can use blue light filters on your devices, switch to warmer light bulbs, or install dimmer switches to control brightness levels.

Although the study provides compelling evidence linking light pollution to Alzheimer’s disease, the researchers emphasize the need for further research. Their analysis was based on data from a subset of the U.S. population, and individual exposure to light pollution can vary significantly. Not everyone lives in high-light environments for their entire lives, and this variability could affect individual risk.

Future studies are needed to better understand the biological mechanisms at play and to explore how long-term exposure to light pollution affects Alzheimer’s risk. With more research, scientists hope to pinpoint the exact pathways through which light pollution impacts brain health and identify more effective interventions.

Note: Materials provided above by The Brighter Side of News. Content may be edited for style and length.

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