A team of University of Michigan mathematicians used a smartphone app that reduces jetlag to gather data on the sleep of thousands of people in 100 nations, revealing the sleep patterns of people around the world and shedding light on the roles of culture and biology in our sleep schedules.

The researchers examined the effects of age, gender, amount of light and home country on the amount of sleep that people around the world get, when they go to bed and when they wake up.

The findings revealed that cultural pressures can trump natural circadian rhythms, which are the fluctuations in bodily functions and behaviors that are connected to the Earth's 24-hour day. These rhythms are set by our brain and regulated by the amount of light that our eyes take in, although as the results reveal, culture can decrease the influence of these factors.

In addition, the effects of cultural pressures on sleep are most prominent at bedtime. Although the amount of morning responsibilities that a person has also plays a role in when they wake up, the team says that these are just some of the important variables.

"Across the board, it appears that society governs bedtime and one's internal clock governs wake time, and a later bedtime is linked to a loss of sleep," said Daniel Forger of the University of Michigan and senior author of the study. "At the same time, we found a strong wake-time effect from users' biological clocks - not just their alarm clocks. These findings help to quantify the tug-of-war between solar and social timekeeping."

Sleep is an important part of any person's life and even missing out on just one or two hours of necessary sleep per night can add up and cause problems later on in life.

"It doesn't take that many days of not getting enough sleep before you're functionally drunk," said Olivia Walch of the University of Michigan and first author of the study. "Researchers have figured out that being overly tired can have that effect."

"And what's terrifying at the same time is that people think they're performing tasks way better than they are," she added. "Your performance drops off but your perception of your performance doesn't."

The findings were published in the May 6 issue of Science Advances.