Researchers in China followed the daylight habits of 87,000 adults for eight years. By the end, 741 of them had developed dementia, and those 741 had logged markedly less sunlight each day than everyone else.
The study, published in the journal General Psychiatry, measured both day and night-time light exposure. The dividing line it found was about 42 minutes. People who averaged less than that outdoors each day were significantly more likely to develop the disease, and the risk fell the longer people stayed out.
Weather did not seem to matter much. Regular time outside on overcast days was linked to a dementia risk up to 16 per cent lower later in life.
Dr Hongliang Feng, of Guangzhou Medical University, said: “Daytime light exposure may serve as a new indicator of dementia risk.”
Nobody can yet say why. Some experts argue the finding runs the other way round: people who are already unwell, and so already at greater risk of dementia, are less likely to leave the house. Others hold that sunlight helps regulate the body’s circadian rhythm, the internal clock that governs sleep and helps clear toxic cells.
The stakes are not small. Nearly a million people in the UK live with dementia, which has no cure and kills more than 75,000 a year. The number is expected to climb as the population ages.
For all the noise about supplements and brain-training apps, the list of things that appear to help is short and rather dull. Regular exercise and socialising. Blood pressure, weight and cholesterol kept in check. There is even research suggesting that wearing glasses or a hearing aid, where needed, lowers the risk. Sunlight exposure could now be added to it.
Sources
- Sunlight could be crucial to preventing dementia, study finds
- Daily Sunlight Linked to Lower Dementia Risk, Study Shows
Sources
- Sunlight could be crucial to preventing dementia, study finds
- Daily Sunlight Linked to Lower Dementia Risk, Study Shows
