Night time light pollution linked to increased Alzheimer’s risk: what a new study says

The disease

Alzheimer’s is the most common type of dementia, an umbrella term for a range of conditions that involve the loss of cognitive functioning. It involves the formation of plaques and tangles in the brain, and the accelerated aging of certain neurons concerned with storage and processing of memory.

Early symptoms include forgetfulness — and as the illness progresses, patients become more confused, lose their way around familiar places, and have difficulties with planning and completing simple tasks.

According to WHO estimates from 2023, more than 55 million people suffer from dementia worldwide, with Alzheimer’s contributing to around 75% of these cases. Anywhere between 3 and 9 million Indians are believed to suffer from the disease, a number that is set to grow as India’s population ages.

Latest drugs may slow down cognitive decline, but there is no cure available yet.

The study

Earlier research has suggested that multiple factors may contribute to Alzheimer’s, from genetics and medical conditions to environmental stresses. The new study adds to this scholarship by introducing a new environmental factor — light pollution — that hasn’t been previously considered.

The study used satellite-acquired light pollution data from the US, and mapped it along with publicly available Medicare data reports on the prevalence of Alzheimer’s. Other medical data on variables known or believed to be risk factors were incorporated into the analysis.

Researchers found that while conditions like diabetes and hypertension were correlated more strongly with the prevalence of Alzheimer’s than night-time light intensity, the latter was more strongly associated with the disease than alcohol abuse, chronic kidney disease, depression, heart failure, and obesity — all commonly cited risk factors.

The correlation with light exposure was more stark when it came to early-onset Alzheimer’s i.e., for those under the age of 65.

Robin Voigt, one of the study’s authors, told The Guardian that exposure to light at night disrupts natural circadian rhythms and hampers sleep, making individuals more susceptible to the disease. Additionally, “disruption of circadian rhythms is associated with increased risk of diseases that are risk factors for Alzheimer’s including obesity, diabetes, and depression,” the study says.

Too much light

As much as 80% of the global population experiences light pollution.

Although these artificial night-time lights are most often seen as harmless — and sometimes even beneficial (for safety, etc.) — recent research has shown numerous negative impacts of these lights, both to humans and the environment. The latest study adds to the growing scholarship on the subject, and raises an issue that should (but currently does not) concern policymakers.