What Is a Normal Night’s Sleep?

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Benjamin Franklin touted “Early to bed, early to rise …” Other sages say 8 hours a night is needed. Odds are, however, that most people reading this article did not do either last night. What makes up a normal night’s rest varies greatly by nationality, sex, age and other factors, according to a new study, that showed a mean sleep duration of 7.88 hours, with variances by age and sex.

People have an internal circadian clock that drives their slumber patterns. The body clock encodes sunrise and sunset, moderated by work obligations and the regular pattern established by the alarm clock. The impact of cultural norms and other things that effect sleep patterns are rarely considered (beyond the fact that television shows for those who still follow such things air earlier in the Central time farm belt). However, cultural pressures, such as work and school, have a large impact on people’s circadian clocks.

The new study, published Friday in “Science Advances,” analyzed the sleep patterns of over 5,000 adults around the world, looking at cultural effects and sleep patterns using a free mobile phone app. Called ENTRAIN (entrainment is the technical/scientific term for adjusting to a different time zone), the app was originally developed to help users overcome jet lag via an algorithm based on daylight patterns. Being used for an international study like this provided a cost-effective trove of data.

“Lab conditions in sleep studies are very regulated, and participants don’t have to deal with the stresses of the real world like spouses, children and all the stuff that keeps us up at night worrying,” explained Danny Forger, a biological mathematician at the college. He also pointed out that a lab-based study “would cost about $20,000 per individual to get this type of information.”

The information on bedtime patterns was input from people in more than 20 countries, with 45 percent coming from the U.S. The participants were mostly between 20 and 70 years old, and approximately three-fifths were male.

The data input indicates that gender does have a role in how long people sleep. Females get 8.07 hours of rest on average daily, whereas males typically get 7.77 hours. To accomplish this, women hit the pillow a little earlier than men do and may wake up slightly later. This is particularly noticeable for those between the ages of 30 to 60. The study also showed that middle-aged men get the least shut-eye.

No surprise, those between 18 and 24 (college-aged adults) go to bed and rise later than older adults. The study authors theorized that this might be because older adults are more sensitive to subconscious prompts from the sun and sleep during set times of day. It could also be, however, because they have more time-dependent responsibilities, such as a regular job schedule or children to get to school, and younger adults tend to be more like an Eveready bunny, going strong until they run out of energy.

Nationality also affects what amount of sleep is normal. People who lived in Japan and Singapore recorded he shortest slumber durations in the study, with participants getting about 7 hours and 24 minutes, on average, of bedtime daily. Those from the Netherlands got the most rest, averaging 8 hours and 12 minutes of rest per night.

“In the real world, bedtime doesn’t behave how it does in our model universe,” noted Olivia Walch, a mathematics doctoral student who developed the app and co-authored the study on what comprises a normal night’s sleep. “What the model is missing is how society affects that,” she added.

Written and Edited by Dyanne Weiss

Science Advances: A global quantification of “normal” sleep schedules using smartphone data
University of Michigan: Smartphones uncover how the world sleeps
TIME: How You Sleep Depends on Where You Live
Los Angeles Times: What is a ‘normal’ night’s sleep? It depends on your age, gender and nationality

Photo courtesy of Joi Ito’s Flickr Page – Creative Commons license