Failing to make up for lost sleep can have fatal consequences for health, according to new research. People who slept more than three hours less than usual and did not catch up on rest the following day faced a death risk up to 42% higher.
A joint research team from Tsinghua University in China and Harvard University in the United States recently published the findings analyzing the relationship between sleep deprivation and recovery sleep in the international journal Nature Communications, the medical community said Wednesday.
The team tracked long-term sleep records of more than 85,000 participants from the UK's large-scale medical data platform Biobank. Participants wore wrist sensors during daily life, and researchers analyzed actual sleep data spanning approximately 570,000 days.
The researchers calculated each participant's required sleep duration based on their individual average sleep time and age- and gender-based averages. Days on which participants slept at least 2.5 hours less than this threshold were defined as a "sleep restriction state." Cases in which participants slept longer than usual the day after sleep deprivation were classified as "recovery sleep" (sleep rebound).
"Can I Just Catch Up on Weekends?"…Late Recovery May Be Less Effective
The findings were more pronounced than expected. The group that slept 2.5 to 3.5 hours less than usual without any meaningful recovery sleep had a 15% higher death risk than those with regular sleep patterns. Notably, those who slept more than 3.5 hours below their usual amount and did not sleep more the following day saw their death risk rise by as much as 42%.
In contrast, those who immediately extended their sleep time the day after sleep deprivation showed different results. The researchers explained that their death risk showed no statistically significant difference from the regular sleep group. The actual recovery sleep averaged about one hour, and most occurred on weekdays rather than weekends.
This suggests that piling up sleep on weekends and holidays may not be a cure-all. The researchers noted that previous studies have raised concerns that excessive weekend sleep could actually disrupt circadian rhythms, and that recovering as quickly as possible after sleep loss may be important.
"Short Sleepers at Greater Risk"…Experts Warn Against Overconfidence in Recovery Sleep
The risks were greater for those who already slept short hours to begin with. The researchers warned that people who routinely sleep little may face a heavier health burden from even a few additional hours of sleep loss. Repeated sleep deprivation increases inflammatory responses in the body, leads to weakened immune function and elevated stress hormones, and may ultimately raise the risk of cardiovascular and metabolic diseases, according to the explanation.
However, experts emphasized that the study should not be interpreted as meaning "you can simply catch up on lost sleep later." Dr. Jean-Philippe Chaput, a sleep expert at the University of Ottawa in Canada, said, "Recovery sleep may reduce some of the risks, but that does not mean it is acceptable to repeat chronic sleep deprivation throughout the week."
