Street lighting and illuminated billboards can help prevent crime, improve road safety and enhance the appearance of the landscape. But they can also have disastrous consequences for our health.
The essence of the night is darkness. But that is no longer the case these days. Our earth is increasingly illuminated at night. In fact, light pollution is increased by at least 49 percent in 25 years. It’s bad news for prey animals. Because when we take away the darkness, we take away what protects many species from predation. But light pollution doesn’t just have ecological consequences. It also turns out to be bad for our health, possibly increasing the risk of Alzheimer’s disease.
Study
The researchers came to this conclusion after studying maps of light pollution in the lower 48 U.S. states. They also looked at medical records of factors known or suspected to be risk factors for Alzheimer’s. They collected data on nighttime light intensity in each state and divided it into five categories, from least to most nighttime light.
Alzheimer
In doing so, they discovered that light pollution is associated with a higher risk of Alzheimer’s disease. Strikingly enough, especially in young people. In people aged 65 and older, Alzheimer’s appears to be more strongly associated with nighttime light pollution than with other factors such as alcohol abuse, chronic kidney disease, depression and obesity. However, other risk factors such as diabetes, high blood pressure and stroke are more strongly associated with Alzheimer’s than light pollution. But in people under 65, the researchers saw a very different pattern: higher exposure to nighttime light appears to be associated with a greater risk of Alzheimer’s than any other risk factor. This suggests that younger people may be more susceptible to the effects of light pollution. “We show that there is a link between the prevalence of Alzheimer’s and exposure to light at night, especially in people under 65,” concludes researcher Robin Voigt-Zuwala. “Nighttime light pollution, an environmental factor that we can modify, may be an important risk factor for Alzheimer’s.”
Mortgage
A pressing question is what exactly underlies the link between light pollution and Alzheimer’s. “I think light pollution affects overall health, including cognitive health, by disrupting the circadian rhythm (see box, ed.),” Voigt-Zuwala explains in an interview with Scientias.nl out. “Our research has shown that this disruption can lead to inflammatory responses in the gut microbiome. This in turn can cause intestinal leakage, which may contribute to neurodegeneration. However, more research is needed to confirm this theory.”
More about the circadian rhythm
The human body has an internal clock, also called the biological clock. This is why we all maintain a day-night rhythm of approximately 24 hours. This rhythm is also called the circadian rhythm (‘approximately one day’). This rhythm plays an important role in the sleep-wake rhythm, but also in a large number of other bodily processes. For example, the biological clock influences processes such as hormone release (including melatonin and cortisol) and glucose management. Various bodily functions, including body temperature, hunger and satiety, are also regulated by the biological clock. The biological clock therefore ensures that the processes in our body take place at the right time. Disruptions in the biological clock can occur due to various causes, such as night work, jet lag or prolonged use of light-emitting screens in the evening.
It’s also not yet clear exactly why younger people might be more vulnerable, but it could have to do with individual differences in how they respond to light. “Some of the genetic factors that influence early-onset Alzheimer’s may also change the way people respond to biological stress, which could explain why they are more sensitive to light at night,” Voigt-Zuwala says. “In addition, younger people are more likely to live in urban areas and have lifestyles that increase their exposure to light at night.”
Licht
Furthermore, it turns out that some types of light have a greater impact than others. “Studies show that blue light (with short wavelengths) has the greatest influence on the circadian rhythm,” Voigt-Zuwala notes. “This is also the light that is best avoided. “Dim light and red light (with long wavelengths) are less disruptive to the circadian rhythm.”
Indoors
By the way, this is not just about outdoor light exposure. Because the researchers suspect that indoor light could be just as important and could also increase the risk of Alzheimer’s. “Indoor light also plays a crucial role,” Voigt-Zuwala emphasizes. “My future research will focus on how exposure to light inside and outside the home affects the cognitive health of older adults.”
Conscious
According to Voigt-Zuwala we should the findings from her study should not be seen as alarming. “But people should be aware of it,” she emphasizes. “This information should encourage people to take steps to reduce their exposure to light at night. And that can be done with simple lifestyle changes.”
According to Voigt-Zuwala, it’s really important that we take the issue seriously. “Reducing nighttime light exposure may help reduce the risk of Alzheimer’s,” she says. “Everyone, especially those at risk due to family history or genetics, should take steps to limit their nighttime light exposure. This can be as simple as hanging blackout curtains or wearing an eye mask while sleeping. This can be particularly helpful for people living in areas with high light pollution. You can also install dimmers, smart bulbs or light switches indoors. If you still have bright blue LED lights in your home, consider replacing them with warm-toned bulbs. It’s also helpful to use blue-light filters on your phone, tablet and computer, and wear blue-light blocking glasses when watching TV. Outdoors, you can remove unnecessary lights or replace them with warmer-toned bulbs. If it’s confirmed that reducing nighttime light exposure really does help reduce the risk of Alzheimer’s, then everyone should take these steps.”