Why Younger People May Be More Vulnerable
Using satellite-acquired data, the study authors calculated average nighttime light intensity by state and county (excluding Hawaii and Alaska) between 2012 and 2018. Drawing on Medicare data, they determined Alzheimer’s disease presence in different regions and compared disease prevalence to the level of light intensity in each area. They also incorporated medical data about variables known or believed to be risk factors for Alzheimer’s.
In comparing risk factors, Dr. Voigt-Zuwala and her colleagues found that Alzheimer’s prevalence in people 65 and older was more strongly linked with nightly light pollution than with alcohol abuse, chronic kidney disease, depression, and obesity. Other risk factors, including diabetes, high blood pressure, and stroke, were more strongly connected with Alzheimer’s than light pollution.
For people under 65, however, nighttime light intensity was the No. 1 influence associated with Alzheimer’s. Because no other disease risk factor in this population was as strongly tied to this dementia, scientists suggested that younger people may be particularly sensitive to the effects of light exposure at night.
Voigt-Zuwala notes that younger people tend to have lifestyles that expose them to more light at night.
“Urban areas with the most light pollution tend to be dominated by younger individuals, and younger people tend to stay up later for social activities,” she says. “Light exposure during the normal rest period will disrupt circadian rhythms and will have detrimental effects on health.”
Less Sleep Equals Greater Dementia Risk
“Beta-amyloid, a biological marker for Alzheimer’s disease, can start to accumulate in the brain decades before symptom onset,” says Dr. Hara, who was not involved in the research. “It is during sleep when toxic proteins such as amyloid get flushed out of the brain. Thus, it may be especially important for middle-aged people to get a sufficient amount of sleep to prevent the accumulation of amyloid and other toxic proteins in the brain.”
Indoor Light at Night From Electronics May Also Pose Risks
Claire Sexton, DPhil, who serves as the senior director of scientific programs and outreach at the Alzheimer’s Association, says that this new paper only takes into account outdoor nighttime light exposure, not indoor, which can also contribute to poor sleep.
Although not investigated in this paper, blue light from electronics may be a major source of trouble when it comes to sleep, according to the study authors.
“Blue light promotes wakefulness and alertness,” says Hara. “When you use electronics in the evenings, they can lead to an inability to fall asleep. Most phones and computers have settings to block the blue light during evening hours.”
Dr. Sexton, who was not involved in the latest research, stresses that the study is “very broad and nonspecific,” and does not demonstrate that light pollution causes Alzheimer’s disease.
“Much more research is needed before conclusions can be made,” she says.
Limiting Light Pollution’s Damaging Effects
Overall, the findings here support previous research, and age-old wisdom, showing that a proper’s night rest is a key to health.
To keep light from disturbing your slumber, the study authors recommend the following:
- Install blackout curtains.
- Wear an eye mask.
- Remove any unnecessary lights outside the home.
- Use light bulbs outdoors that are warmer and less harsh.
