A study in General Psychiatry that tracked light exposure with wrist devices found brighter daytime light associated with lower dementia risk, though researchers stress it shows an association, not a cause.
A study published in General Psychiatry has linked brighter daytime light exposure to a lower likelihood of developing dementia. Researchers analysed data from 87,577 adults who wore wrist devices with accelerometers that measured light exposure by day and by night. Over a median follow-up of 8.1 years, 741 participants developed dementia. People whose average daytime light exceeded 1,000 lux, a level comparable to an overcast day outdoors, had a 16% lower risk, and longer time in light of at least 5,000 lux was associated with further reductions.
The team also reported that getting less than 0.7 hours, or 42 minutes, of bright daytime light each day was a stronger predictor of dementia than six established risk factors. By contrast, they found no statistically significant link between nighttime light exposure and dementia risk, which suggests that daytime brightness may be the relevant part of the relationship. Corresponding author Hongliang Feng of Guangzhou Medical University said daytime light exposure may serve as a novel indicator of dementia risk.
The findings describe an association and do not show that more daylight prevents dementia. The authors present daytime light as a potentially useful indicator of risk that deserves further investigation, not as a proven way to lower it. The results were reported in a Wiley press release carried by ScienceDaily, so readers should consult the full paper for how other factors were accounted for, and anyone worried about memory or dementia risk should speak to a doctor.
