Excessive light pollution at night may increase the risk of Alzheimer’s disease – especially in younger people, warns a new study.
Researchers found that exposure to outdoor light after dark could increase the prevalence of dementia more than many other risk factors for people under 65.
In some places around the world, the lights never go off.
Streetlights and illuminated signs can deter crime and make roads safer.
But scientists say undisrupted light comes with ecological, behavioral, and health consequences.
American researchers investigated correlations between outside nightly light pollution and Alzheimer’s disease.
Study first author Professor Robin Voigt-Zuwala of Rush University Medical Center in Chicago, said: “We show that in the US, there is a positive association between Alzheimer’s disease prevalence and exposure to light at night, particularly in those under the age of 65.
“Nightly light pollution – a modifiable environmental factor – may be an important risk factor for Alzheimer’s.”
The researchers studied light pollution maps of the lower 48 US states and incorporated medical data about variables known or believed to be risk factors for Alzheimer’s in their analysis.
They generated night-time intensity data for every state and divided them into five groups, from lowest to highest night-time light intensity.
Their findings, published in the journal Frontiers in Neuroscience, showed that for people aged 65 and older, Alzheimer’s prevalence was more strongly correlated with nightly light pollution than some other disease factors – including alcohol abuse, chronic kidney disease, depression, and obesity.
Other risk factors – such as diabetes, high blood pressure, and stroke – were more strongly associated with Alzheimer’s than light pollution.
But for people aged under 65, the researchers found that higher night-time light intensity was associated with a greater Alzheimer’s prevalence than any other risk factor examined in the study.
The researchers say it could suggest that younger people may be “particularly sensitive” to the effects of light exposure at night.
It is unclear why younger people could be more vulnerable, but the research team believes it could be due to individual differences in light sensitivity.
Voigt-Zuwala said: “Certain genotypes, which influence early-onset Alzheimer’s, impact the response to biological stressors which could account for increased vulnerability to the effects of night-time light exposure.
“Additionally, younger people are more likely to live in urban areas and have lifestyles that may increase exposure to light at night.”
The researchers hope that their findings can help educate people about the potential risks of light at night.
Voigt-Zuwala said: “Awareness of the association should empower people – particularly those with risk factors for Alzheimer’s – to make easy lifestyle changes.”
She added: “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.”
The researchers say light exposure inside the home could be as important as light exposure from outside.
Although they didn’t examine the effects of inside light in the study, the team said that blue light has the greatest impact on sleep, and using blue light filters, swapping to warm light, and installing dimmers in the home could effectively reduce light exposure.
Produced in association with SWNS Talker
