Light Pollution Linked To Higher Alzheimer's Risk In Youngsters, Study Suggests

Artificial light, while crucial for modern living, can significantly affect human health. Night-time exposure to artificial light disrupts the body's natural circadian rhythm. This disruption can lead to sleep disorders, depression, and an increased risk of chronic conditions such as obesity and diabetes.

In urban areas worldwide, lights often remain on throughout the night. Streetlights, roadway lighting, and illuminated signs help deter crime, improve road safety, and enhance landscaping. However, continuous light exposure has ecological, behavioural, and health consequences.

In the US, some states have laws to reduce light pollution; however, night-time light levels remain high in many regions. Researchers have now explored links between outdoor night-time light pollution and Alzheimer's disease (AD). "We show that in the US there is a positive association between AD prevalence and exposure to light at night, particularly in those under the age of 65," said Dr. Robin Voigt-Zuwala from Rush University Medical Center. "Nightly light pollution—a modifiable environmental factor—may be an important risk factor for AD."

The study was published in Frontiers in Neuroscience.

The researchers analysed light pollution maps of the lower 48 US states alongside medical data on known or suspected AD risk factors. They generated night-time intensity data for each state and categorised them into five groups based on light intensity levels.

The findings indicated that for individuals aged 65 and older, AD prevalence was more strongly linked to nightly light pollution than other disease factors like alcohol abuse, chronic kidney disease, depression, and obesity. However, diabetes, high blood pressure, and stroke had stronger associations with AD than light pollution.

For those under 65, higher night-time light intensity correlated with greater AD prevalence than any other risk factor examined. This suggests younger people might be particularly sensitive to night-time light exposure effects.

The reason younger individuals might be more vulnerable remains unclear but could relate to differences in light sensitivity. "Certain genotypes influencing early-onset AD may impact responses to biological stressors," Voigt-Zuwala explained. "Additionally, younger people are more likely to live in urban areas with lifestyles increasing night-time light exposure."

The researchers hope their findings will raise awareness about the risks of night-time light exposure. "Awareness should empower people—especially those at risk for AD—to make simple lifestyle changes," Voigt-Zuwala stated. "Using blackout curtains or eye masks can help those in high-light-pollution areas."

Moreover, indoor light exposure could be as significant as outdoor exposure. Although not examined in this study, blue light has the most substantial impact on sleep. Using blue light filters, switching to warm lights, and installing dimmers could effectively reduce indoor light exposure.

The researchers noted their results are based on a subset of the US population and that not everyone lives in high-light-pollution areas their entire lives—both factors could affect individual outcomes. Further research is needed to understand how night-time light influences AD fully.