Too short or too long outdoor lighting can increase the risk of dementia

Recently, a study conducted by Professor Yu Jintai of Huashan Hospital Affiliated to Fudan University and Professor Tan Lan of Qingdao Municipal Hospital Affiliated to Qingdao University found that a study of more than 360,000 people and a 9-year follow-up study found that proper sun exposure helped prevent Alzheimer’s disease. The study reveals for the first time the relationship between outdoor light duration and dementia, providing new ideas for the prevention of dementia. The results of the research have been published in the latest issue of the British Medical Council – Internal Medicine.

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Proper sun exposure helps prevent Alzheimer’s disease Courtesy of respondents

“Light is one of the most important factors affecting the rhythm of the biological clock. Changes in light conditions send signals to the circadian clock structure in the brain through visual pathways, which in turn adjust the rhythms of physiology and behavior. At the same time, light can also affect brain function through non-visual pathways. Yu Jintai told China Science Daily, “But there have been no large-scale cohort studies to reveal the relationship between light duration and dementia.”

To get this straight, the team used the UK Biobank cohort to include 362094 non-dementia participants aged 37 to 73 who were followed up for an average of 9 years. All participants separately reported on the average amount of time they received outdoor light each day during the summer and winter seasons.

During a 9-year follow-up period, a total of 4149 participants were found to be diagnosed with new-onset dementia. The study found a typical nonlinear “J-shaped” relationship between outdoor light duration and dementia, that is, too short or too long outdoor light time will increase the risk of dementia.

“The optimal outdoor light duration is 2 hours per day in summer and 1 hour per day in winter, with an average of 1.5 hours per day.” Yu Jintai said.

The study found that for every 0.5 hours of outdoor lighting, the risk of dementia increased by 28.7%, and for every 0.5 hours of outdoor lighting, the risk of dementia increased by 7.0% for every 0.5 hours of outdoor lighting. Outdoor light time is shorter than optimal outdoor light time, which increases the risk of dementia. This result is more pronounced in older people aged about 60 years.

“Outdoor light prevents the onset of dementia by influencing vitamin D in the body, which is involved in many key pathways of brain health, including neuroprotective, immune response regulation, inhibition of inflammation, and regulation of oxidative stress.” When talking about the mechanism of outdoor light and dementia, Tan Lan introduced, “Outdoor light also regulates the circadian rhythm by acting on the internal clock of the human body – the optic chirodate nucleus, which affects cognitive function. ”

In the next step, the researchers will further clarify the potential association between outdoor light and dementia through experiments. (Source: China Science Daily, Zhang Shuanghu, Huang Xin)

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