Emily Chan
They ranged in age from 18 to 80 and were almost equally represented across age groups and gender.
The researchers asked each individual to fill out a daily survey about their sunlight exposure and sleep quality. The surveys were completed between 8:30 PM and midnight local time.
Participants made sure to note how long they spent outside in direct sunlight and at what time of day they were outside. A modified version of the Pittsburgh Sleep Quality Index was used to measure sleep quality.
The researchers employed a statistical method called multilevel modeling to control for factors that could influence sleep, such as health, age, and whether the day was a weekday or weekend. It helped them identify long-term sleep patterns and daily fluctuations.
The study found that morning sunlight exposure led to better sleep quality that night. People who went outside in the morning reported falling asleep more quickly, longer sleep time, and fewer awakenings during the night. Additionally, their sleep efficiency (how much of the time they spent lying in bed asleep) was higher.
The amount of time that participants spent in the sun each day did not have much of an impact on sleep quality, suggesting that the specific timing of sun exposure was what mattered most when it came to promoting better sleep. Morning sunlight may help regulate circadian rhythms, leading to improved sleep quality.
There were no strong links between midday or evening sunlight exposure and sleep quality. Some individuals who spent time in evening sunlight actually woke up earlier the next morning.
Hopefully, future studies can go more in-depth into the benefits of morning sunlight exposure, accounting for factors like geographical location, season, skin pigmentation, and artificial light exposure.
The study was published in the Journal of Health Psychology.
