Photo: C_Scott via Pixabay, CC0 Photo: C_Scott via Pixabay, CC0

It’s well known that not getting enough sleep can harm you in a variety of ways, including increasing your risk of mortality. However, new research published in the Journal of Sleep Research suggests that catching up on sleep over the weekend may be able to help you stave off some of the negative effects of sleep deprivation.

Catching Up On Sleep?

A research team looked at the sleep patterns and relative health of adults under the age of 65 who got less than five hours of sleep for seven days a week, and found that they had a notably higher risk of death compared to those who got between 6 to 7 hours of sleep most nights. Yet the study also found that the individuals who got less sleep during the week but then slept longer on the weekends didn’t see an increase in their mortality risk when compared with the same group of people who slept 6 to 7 hours.

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After the researchers controlled for a variety of different variables such as smoking, general physical activity, gender, hours of work, and body mass index, the results of the study implied that people under the age of 65 who got less than five hours of sleep during the week had a mortality rate 65% greater than those who slept between 6 to 7 hours during the week. Crucially though, this increased mortality rate was not observed in those who slept less than five hours during weekdays but managed to sleep eight hours or more on the weekends.

The study is the culmination of 13 years worth of studying over 38,000 adults in Sweden. Lifestyle and medical data were collected on the participants back in 1997, and researchers continue to track the participants over the next 13 years. A national death register was used to see which participants had died.

Torbjörn Åkerstedt, the study’s lead author and researcher at the Stress Research Institute at Stockholm University explained that previous studies that only examine the link between mortality and sleep duration during the week, but that he suspected that the results would change if one accounted for how much people slept on the weekends.

While the researchers found that too little sleep could easily increase people’s risk of mortality, they also found that too much sleep could also have a negative effect on people’s health and increase one’s risk for mortality. According to the study, those who slept for eight or more hours seven days a week had a mortality rate that was approximately 25% higher when compared to those who slept between 6 to 7 hours every day of the week.

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The researchers noted that the correlations with sleep time and mortality rate seemed to disappear for people age 65 or older, which could be because older people are more likely to be able to get the amount of sleep they need. The number of people saying they didn’t feel well rested upon waking, as well as the average amount of time spent asleep on weekends seems to decrease with age as well.

Unknown Mechanisms

According to Åkerstedt, the exact causal mechanism between why both too much sleep and too little sleep are correlated with higher mortality rates is unknown, though the hypothesis is that too little sleep probably has a negative effect on the body overall, while too much sleep can be indicative of other health problems.

Åkerstedt also thinks that short duration sleepers are likely changing their day-to-day habits on the weekends, which helps make up for some of their lost sleep during the week. To put that another way, it’s not that you can store up sleep but that if you get slightly less than six hours during the day, you might be able to compensate for it by sleeping longer on the weekends. This only works if there isn’t too great of a sleep deficit, however.

The study seems to contradict earlier research on the possibility of catching up on sleep. A prior study done at Harvard found that one couldn’t really stave off the effects of sleep deprivation by getting a night of “catch-up” sleep. It was found that even with the ability to sleep 10 hours after consecutive days of sleep deprivation, participants were still suffering and performed worse at cognitive tests and reaction timing tests than those who were well rested.

A Word Of Caution

Indeed, Dr. David Dinges, head of the sleep and chronobiology division at University of Pennsylvania Perelman School of Medicine says that while the results of the study are interesting, people should still be cautious about shirking sleep. Dinges warns that there’s still very little research on “yo-yo sleeping” and that more studies will have to be done. Dinges says that while 13 years is a long time, it’s not 30 or 40 years and that damage could be cumulative over a long time frame, even if you’re getting recovery sleep.

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Åkerstedt says that although the study seems to provide evidence that the weekend sleep is catch-up sleep, the study cannot definitively prove that to be correct. One of the study limitations was that its participants were only polled about their sleep patterns at one specific point in time, and not continually throughout the duration of the study.

Despite this, Stuart Peirson (not involved in the research), an expert on the human body’s circadian rhythm (or natural clock) opined that the study granted deeper insight into the relationship between sleep and health. Says Peirson:

It fits with what we do know about sleep – that sleep is regulated by the body clock but also regulated by what is called a homeostatic process, which means the longer you are awake the more you need to sleep.

Åkerstedt notes that the 7-hour guideline is just that, a guideline, not a hard rule. People are individuals, and some people require more sleep than other people. Åkerstedt seems to suggests listening to your body and that if you can (genuinely) function on the sleep you’re getting, you’re probably getting enough. Still, Åkerstedt has a theory about why the new study has attracted so much more attention than his previous sleep research. He says that people may want to believe the study because it gives them an excuse to sleep in on their off days. People are just attracted to the idea that they can actually compensate for their lost sleep during the week, Åkerstedt said.

“Perhaps it’s giving them hope that this habit is in some way good for them,” said Åkerstedt.