Artificial light at night (ALAN) doesn’t just contribute to sky pollution — it may also have damaging effects on the brain. A recent study highlights a potential link between light pollution and an increased risk of Alzheimer’s disease (AD), raising concerns about how modern urban environments could be affecting public health.
Alzheimer’s Disease and Its Impact
According to the Alzheimer’s Association, Alzheimer's is the most common form of dementia, accounting for 60–80% of cases. It is a progressive condition, typically impacting individuals over 65, with symptoms such as memory loss and an inability to perform daily activities. While not considered a natural part of ageing, it remains a significant risk for older populations.
A study led by Robin Voigt-Zuwala, an associate professor at Rush University Medical Center, indicates that ALAN could be a major contributor to the development of Alzheimer’s. The findings, published in Frontiers in Neuroscience, show a strong correlation between exposure to excessive nighttime light and higher rates of Alzheimer's.
The study reports, “Higher outdoor nighttime light was associated with higher prevalence of AD,” suggesting that light pollution may pose a greater risk to cognitive health than previously understood. Although factors like atrial fibrillation and diabetes were more strongly associated with Alzheimer’s, nighttime light exposure was still a significant factor, surpassing others such as alcohol abuse, depression, and heart failure.
Younger Populations at Greater Risk
One of the most striking aspects of the study is the observation that individuals under the age of 65 seem particularly vulnerable to light pollution. “Nighttime light exposure is more strongly associated with AD prevalence in those under the age of 65 than any other disease factor examined,” the researchers state.
This may be due to genetic factors that make younger individuals more susceptible to Alzheimer’s, such as variations in the APOE gene, which is known to increase early-onset Alzheimer’s risk. Additionally, the disruption of circadian rhythms — the body’s natural clock that governs sleep-wake cycles — may play a significant role. Voigt-Zuwala points out that younger people are more likely to live in urban settings and maintain lifestyles that expose them to higher levels of artificial light.
The Role of Inflammation in Alzheimer’s Progression
Prolonged exposure to artificial light can interfere with natural circadian rhythms, potentially leading to inflammation in the brain. This inflammation, in turn, may stimulate the production of Beta-amyloid, a protein heavily implicated in Alzheimer’s development.
The study further supports this by referencing animal research, which shows that mice exposed to dim light experienced an increase in pro-inflammatory chemicals. These mice also had lower levels of brain-derived neurotrophic factor (BDNF), a protein crucial for maintaining cognitive function. Reduced BDNF in areas of the brain, such as the hippocampus, is known to precede cognitive decline, suggesting that inflammation triggered by nighttime light may accelerate Alzheimer’s progression.
Further Research Needed
Kallol Kumar Bhattacharyya, a research fellow at Utah State University, notes that while the study’s results are compelling, more research is required to establish a definitive link between light pollution and Alzheimer’s. Long-term studies and data from different global regions will help to clarify the connection.
For now, this study offers valuable insights into the potentially harmful effects of ALAN, especially for younger individuals. As urbanization continues, addressing light pollution may become an important step in reducing the risk of neurodegenerative diseases like Alzheimer's.