Dementia is one of the fastest-growing health challenges in the world. Millions of people are currently living with the condition, and the number is expected to rise sharply as populations continue to age.
Dementia is not a single disease. Instead, it is a group of conditions that gradually damage memory, thinking, language, and the ability to perform everyday activities.
The most common form of dementia is Alzheimer’s disease, but there are several other types as well. Although age is the biggest risk factor, scientists have learned that lifestyle and environmental factors also influence a person’s chances of developing dementia.
Researchers have already identified several factors that can affect brain health, including high blood pressure, diabetes, smoking, obesity, physical inactivity, social isolation, and hearing loss.
Now, a new study published in the journal General Psychiatry suggests that something as simple as exposure to daylight may also play an important role in protecting the brain.
The study was carried out by researchers who wanted to investigate whether the amount of light people are exposed to during the day and night might influence their risk of developing dementia. Light is essential for much more than vision.
It helps regulate the body’s internal clock, known as the circadian rhythm. This internal clock controls sleep patterns, hormone release, body temperature, and many other important functions.
Scientists have increasingly recognized that disturbances in circadian rhythms and sleep may contribute to brain aging and dementia.
Poor sleep has been linked to memory problems and changes in the brain that are associated with Alzheimer’s disease. Because daylight helps keep the body’s internal clock functioning properly, researchers wondered whether people who spend more time in bright light might have healthier brains.
To explore this idea, the researchers studied 87,577 adults. Participants wore devices called accelerometers on their wrists. These devices can measure movement as well as the amount of light people are exposed to throughout the day and night.
The participants were then followed for a median of 8.1 years. During this period, 741 people developed dementia.
When the researchers analyzed the data, they discovered a clear pattern. People who were exposed to an average daytime light level above 1,000 lux had a 16 percent lower risk of developing dementia compared with those exposed to lower levels of light. A light level of 1,000 lux is roughly similar to a moderately bright, overcast day outdoors.
The benefits appeared to become even greater with brighter light exposure. People who spent longer periods of time in light levels of at least 5,000 lux experienced an additional reduction in dementia risk. This amount of light is usually experienced outdoors during the daytime.
One particularly interesting finding was that getting less than 0.7 hours of bright daytime light per day was a stronger predictor of dementia than six already established dementia risk factors. This suggests that regular exposure to daylight may be much more important for brain health than many people realize.
The researchers also examined nighttime light exposure. Unlike daytime light, exposure to light at night did not show a significant relationship with dementia risk in this study.
The researchers believe several explanations are possible. Bright daytime light helps maintain healthy circadian rhythms and supports better sleep quality.
Good sleep is essential because the brain performs important maintenance activities during sleep, including clearing away waste products that may contribute to neurodegenerative diseases. Daylight exposure may also encourage people to spend more time outdoors, exercise more, and remain socially active, all of which have been linked to healthier brain aging.
Dr. Hongliang Feng of Guangzhou Medical University, the corresponding author of the study, suggested that daytime light exposure may serve as a new indicator of dementia risk.
When reviewing these findings, it is important to remember that the study does not prove that brighter daylight directly prevents dementia. The research only shows an association between light exposure and dementia risk. People who spend more time outdoors may also engage in other healthy behaviors that contribute to better brain health.
Nevertheless, the study involved a very large number of participants and followed them for more than eight years, giving the findings considerable strength. The results add to growing evidence that simple daily habits, including regular exposure to natural daylight, may play an important role in maintaining brain health as people grow older.
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Source: Guangzhou Medical University.
