"Do You Really Need 8 Hours of Sleep?"... Sleep Common Sense Overturned by Data from 270,000 People

Joint Study by Samsung Medical Center, Samsung Electronics, and Harvard Medical School
"The Concept of Uniform Recommended Sleep Duration Does Not Reflect Reality"

"You need to sleep 7 to 8 hours a day to be healthy."

Not related to specific content of the article. Getty Images

This sleep formula, long accepted as common sense, is now being questioned. The largest-ever wearable device study analyzing real sleep data from Samsung Galaxy Watch users has newly confirmed that the amount of sleep needed varies greatly from person to person.

According to Yonhap News Agency and the latest issue of the international journal 'SLEEP' on June 27, a joint research team from Sungshin Women's University, Samsung Medical Center, Samsung Electronics, and Harvard Medical School published a study based on the sleep data of 274,128 healthy adults in the United States who wore Samsung Galaxy Watches.

The key feature of this study is that it objectively tracked, over the long term, how much people actually sleep in daily life outside of a hospital setting. Previous sleep studies often relied on surveys of several hundred to a few thousand people or limited laboratory tests, but this research analyzed the real-world sleep patterns of hundreds of thousands of people using smartwatches equipped with the same algorithm.

Samsung Galaxy Watch4

As a result, the researchers judged that the existing idea of a "one-size-fits-all recommended sleep duration" may not reflect reality. In fact, the average total sleep time was 7 hours and 34 minutes, but individual differences were significant. The 10th to 90th percentile range for all participants' sleep durations stretched from 6 hours and 30 minutes to 9 hours. Among healthy adults, daily sleep time differed by more than 2 hours.

The research team concluded that sleep duration is highly individual, and that there is no single "correct sleep duration" that applies to everyone.

Seo Suyeon, professor of psychology at Sungshin Women's University and the corresponding author of the paper, said, "While it is generally recommended to sleep 7 to 8 hours a day, analysis of big data using the Galaxy Watch shows that there is no single 'right' amount of sleep that applies to everyone," adding, "Rather than fixating on a specific number, it is more important to consider whether you feel sufficiently rested and are functioning well during the day."

The study also produced results that contradicted the conventional wisdom that "sleep decreases with age." Among Americans, the age group that slept the least was not the elderly but those in their 40s. The average sleep duration for people aged 40 to 49 was 7 hours and 32 minutes, the shortest among all age groups. Notably, 25.1% of this group slept less than 7 hours a day.

Those in their 40s also showed the strongest tendency to catch up on lost sleep over the weekend. Their weekend sleep duration increased by an average of 34 minutes compared to weekdays, the largest increase among all age groups. In contrast, the average sleep time for those aged 60 to 69 was 7 hours and 45 minutes, the longest. Overall, a "U-shaped pattern" was observed: both younger and older groups slept longer, while middle-aged adults had the shortest sleep duration. By gender, women slept about 18 minutes longer than men on average across all age groups.

This study is also significant in that consumer wearables like smartwatches are evolving from simple health management tools into actual platforms for medical research. The research team estimated that the sleep measurements from the Samsung Galaxy Watch had an average error of less than 10 minutes compared to hospital-standard polysomnography tests.

Eric Zhou, a sleep medicine specialist at Harvard Medical School, said, "The distribution of sleep standards presented in this study can serve as a practical reference for doctors when consulting patients or when developing public health sleep recommendations in the future."

This content was produced with the assistance of AI translation services.