A new research, by a team from the University of Michigan, reveals the factors that affect people’s sleep cycles. The study was published on May 6, in Science Advances.

The most important contributing factors they found were age, gender, home nation and amount of light exposure. According to the study, people usually set schedules between seven and eight hours of sleep a night, with a mean of 7.88 hours.

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A sculpture entitled “Mask II” by sculptor Ron Mueck, at the San Ildefonso Museum in Mexico City, on September 20, 2011. Photo: Reuters/Henry Romero

Danny Forger, a biological mathematician at the University of Michigan said that people think there are guidelines for sleep cycles, like 8 hours or 7 hours. In contrast, the study found that normal sleep depends on different factors like age, sex and what country you are in.

Contributing factors to sleep cycles

The research team found that gender plays an important role in sleep cycles. The found that, on average, women schedule 8.07 hours of sleep, while men schedule 7.77 hours. Women go to sleep earlier and wake up later than man. The study authors concluded that women schedule more sleep than men.

Age was also found to be an important factor, revealing that older people schedule sleep earlier that younger people, on average. The reason behind this may be that older people are more sensitive to solar cues that younger people like college students. Also, older people seem to only be able to sleep during certain times of the day.

A third factor the team found relevant was nationality since they found that people in Singapore and Japan had a sleep schedule of 7.24 hours, on average. These were the shortest sleep schedules of the 20 countries represented in the study. In the Netherlands, people show to have a schedule of 8.12 hours, on average. In the United States, the average of sleep is 7.87 hours.

Light exposure seems to affect sleep schedules as well. According to the study, People who spend more time in the sunlight each day than those that spend more time in the indoor light, tend to go to sleep earlier and get more sleep. Despite curtains, artificial lights and alarm clocks, the time of sunrise and sunset have a significant effect on sleep patterns.

“We recognize that these solar effects are dulled compared to predictive models, but the fact that they are still there in the data was pretty shocking to me,” said Amy Cochran, an assistant professor at the University of Michigan who also worked on the study.

ENTRAIN app

The smartphone app was launched in 2014, and it is supposed to help people decrease the effects of jetlag. It was designed by Olivia Walch, a graduate student in Forger’s group.

The app works with the help of complex algorithms based on Forger’s previous research. It tells people how to minimize the effects of Jetlag by recommending custom schedules of light and darkness. It tells them when to avoid and expose themselves to light.

The quality of the app depends on the accuracy of the data the app provides. The app encourages users to update information with caution.

How the study was conducted

Forger and his co-workers gather data from the app, to have an overview of the solar cues that influence people. The team used the app and a math modeling to determine the impacts of other factors.

They were able to gather information from thousands of people, which was useful to analyze patterns. The data was put to the test to see what stimulated the brain cells behind the eyes that manage internal body clocks. They tried to find a correlation between the sun up and down with the brain cells, even in extreme conditions.

The authors describe in the study what they considered a normal sleep. They generated hypotheses and suggestions for further investigations and additional laboratory work.

Source: Tech Times