A lack of bright daylight is a more significant risk factor for developing dementia than alcohol or obesity, SciTechDaily reports, according to infohub.kz.
Researchers conducted a large-scale study involving nearly 88,000 people who wore outdoor light sensors for a week. Observations spanning more than eight years showed that people with high daily levels of daylight had a 16–17% lower risk of developing dementia. To gain the benefit, it is enough to spend at least 42 minutes a day in bright light.
The researchers compared light levels of 1,000 lux, which corresponds to an overcast day outdoors, with brighter conditions of 5,000 lux and above. They found that dim daylight predicts the onset of problems with memory and thinking more accurately than well-known risk factors such as traumatic brain injury, alcohol consumption or excess weight. Night-time lighting, meanwhile, showed no significant effect on the development of the disease.
The authors attribute the link to circadian rhythms — the body's internal biological clock that regulates sleep, activity and brain function. A lack of light disrupts these rhythms, with the strongest effect seen in night owls and people with a genetic predisposition to Alzheimer's disease. The researchers note that the study is observational, so walks in the fresh air cannot yet be described as a direct way to prevent dementia.