While the world focuses on plastic waste, chemical pollutants in oceans and smog-filled air, one sneaky culprit often goes unnoticed: light pollution.
Humans are designed to live in a 24-hour cycle where light and darkness follow a natural diurnal rhythm. Light is crucial in regulating our circadian rhythm―our internal clock that tells us when to be awake and when to rest. It also influences melatonin production, a hormone vital for sleep.
The relationship between circadian rhythms and nighttime light exposure is profound. Circadian rhythm governs essential body functions like sleep-wake cycles, hormone regulation and metabolism. The suprachiasmatic nucleus in the hypothalamus acts as the master clock, aligning these processes with external light-dark cycles. However, exposure to artificial light at night, particularly blue light, disrupts this balance. It suppresses melatonin production, making it harder to fall asleep and lowering sleep quality. This disruption can lead to a range of health problems, including sleep disorders, mood swings and metabolic imbalances.
Notably, researchers at Rush University System for Health in the US recently established that there is a link between nighttime outdoor light and Alzheimer’s disease. Researchers warn that an exposure to high levels of light pollution at night could significantly increase the risk of Alzheimer’s, especially in adults under the age of 65.
The study analysed data from 48 American states, correlating nighttime light pollution with the prevalence of Alzheimer’s disease. Researchers examined light pollution maps and incorporated medical data on Alzheimer’s risk factors, categorising groups based on varying levels of light intensity. They uncovered a connection between light exposure, disrupted circadian rhythms and Alzheimer’s risk. Excessive nighttime light can disturb circadian rhythms, leading to inflammation, which heightens susceptibility to diseases like Alzheimer’s.
Dr Robin Voigt-Zuwala, the lead investigator, noted that certain genetic factors associated with early-onset Alzheimer’s may also increase sensitivity to nighttime light exposure. Younger individuals, often living in urban areas with higher light pollution and modern lifestyles that increase nighttime light exposure, were found to be particularly at risk.
Fortunately, the researchers suggest that simple measures, such as installing blackout curtains or using an eye mask while sleeping, can reduce exposure to nighttime light. However, they are yet to study the effects of indoor lighting at night or how it may impact health. So far, the evidence is limited to the US population, and they emphasise the need for further research to fully understand the connection between outdoor light pollution and Alzheimer’s across demographics.