Light has come from natural sources for almost our entire existence on planet Earth. Today, artificial lighting is everywhere, both inside and outside our homes, skewing our biology and fostering a long list of health issues.
Until now, Alzheimer’s has been missing from the list, but not anymore. Researchers are pointing to this kind of artificial light as a new risk factor for Alzheimer’s and dementia. Worse, they’re the BIGGEST risk factor for those under 65.
Key Takeaways
- Nighttime light exposure, specifically streetlights, is now considered a significant risk factor for Alzheimer's, especially in younger individuals.
- Light pollution disrupts circadian rhythms and contributes to poor sleep quality, both linked to increased Alzheimer's risk.
- Using blackout curtains and eye masks and advocating for outdoor light pollution reduction can help minimize exposure.
#1 Risk Factor For Alzheimer’s In Younger People
We can’t live without artificial outdoor lighting, but studies reveal excessive artificial light at night disrupts sleep and promotes obesity, depression, anxiety, atherosclerosis, and cancer. Few studies have looked at the impact of nighttime light pollution on the human brain but one from China and another from Italy found higher risks of developing mild cognitive impairment and late-onset dementia.
Since no study looked specifically at Alzheimer’s, scientists from Rush University Medical Center, Chicago, decided to take a closer look. What they uncovered spooked them.
More Harmful Than Alcohol Abuse and Obesity
The research team acquired satellite data for all states bar Alaska and Hawaii and then mapped out each state’s nighttime light intensity, dividing it into five segments from lowest to highest. They then connected the light spectrum to Medicare data for known Alzheimer’s risk factors.
Results showed the higher the state’s average light intensity, the higher the prevalence of Alzheimer's. For seniors, they found nightly light pollution was linked to Alzheimer's more strongly than alcohol abuse, chronic kidney disease, heart failure, depression, and obesity but less strongly than diabetes, high blood pressure, atrial fibrillation, stroke, and high levels of unhealthy blood fats.
But what alarmed the researchers was the finding for people under 65.
Streetlighting has not only become a new risk factor for Alzheimer’s, but alarmingly, it’s the biggest risk factor for those under the age of 65.
Younger People are More Exposed
In their paper, published in the journal Frontiers in Neuroscience in September, they wrote: “Startlingly, nighttime light exposure is more strongly associated with Alzheimer’s prevalence in those under the age of 65 than any other disease factor examined.”
To explain this difference between the two age groups, Dr. Robin Voigt-Zuwala, who led the study, suggested that “younger people are more likely to live in urban areas and have lifestyles that may increase exposure to light at night.”
Previous research found women, those with less education, and people who shy away from social activities are especially sensitive to light pollution at night. But why is artificial light a problem? The researchers scratched their heads to come up with some answers.
Circadian Rhythm Disruption and Poor Sleep
Scrolling through the research literature, they found people who are genetically predisposed to Alzheimer’s may be more vulnerable to biological stressors like free radicals, and these stressors could account for the increased vulnerability to nighttime light exposure.
Exposure to dim light during dark periods in fruit flies and mice promotes neurodegeneration, and even in humans, long-term exposure to outdoor light at night has been linked to an increased risk of cognitive impairment.
A factor that harms the brain in many ways is sleep disruption. People with insomnia and poor-quality sleep have a higher risk of cognitive impairment and Alzheimer’s. Another factor linked to poor sleep is disruption to the sleep/wake cycle or circadian rhythm. Changes in circadian rhythm often come before Alzheimer’s symptoms. They are linked to an increased risk of diseases that are risk factors for Alzheimer’s, such as obesity, diabetes, and depression, among many others.
Lastly, rodent research found exposure to dim light increases the production of the pro-inflammatory cytokine interleukin 1β, a feature of Alzheimer’s. When mice are exposed to dim light during their dark period, this decreases levels of the brain's 'growth hormone', BDNF, in the hippocampus, a key memory area. Low BDNF has been shown to precede cognitive impairment.
Cutting down on light pollution seems like a good idea, and Dr. Voigt-Zuwala gave two suggestions on how to do this.
Cut Out Light in the Bedroom
He suggested adding blackout curtains or sleeping with an eye mask. These are helpful suggestions if you’re affected by light in the bedroom, but there’s little you can do about exposure outside the home.
States are aware of the light pollution problem, and 17 states have legislation to reduce it. If yours is not among them, contacting your political representative is one action you could take.
Of course, light pollution also occurs inside the home. Still, no indoor light data was available to the Rush research team even though they accept that exposure from televisions, computers, and phones is “critically important” and needs to be evaluated.
Summary
Artificial light at night (ALAN) has been identified as a significant risk factor for Alzheimer's disease, especially in those under 65. Studies reveal that excessive nighttime light exposure disrupts circadian rhythms and poor sleep, which are linked to cognitive decline. Researchers from Rush University found ALAN to be a more potent risk factor than obesity or alcohol abuse. Reducing light pollution inside and outside the home could help lower Alzheimer's risk.
Frequently Asked Questions
- How does artificial light at night increase the risk of Alzheimer’s? Artificial light disrupts circadian rhythms and sleep, both of which are linked to an increased risk of Alzheimer's and cognitive impairment.
- Is nighttime light pollution worse for people under 65? Yes, research shows that people under 65 are more vulnerable to the effects of nighttime light exposure, making it the biggest risk factor for Alzheimer's in this age group.
- What can I do to reduce nighttime light exposure? Use blackout curtains, sleep with an eye mask, and limit exposure to light-emitting devices like phones and computers before bed.
- Are there laws to reduce light pollution? Seventeen U.S. states have implemented legislation to reduce outdoor light pollution, and individuals can advocate for more regulations in their areas.
