4 scientific reasons why sleep is so closely linked to death

You can sleep when you’re dead, but too little sleep may also bring you closer to, well, death.

It may be a morbid idea, but that doesn’t make it untrue. Sleep, countless studies show, is essential. Fragmented sleep both leads to future stress and prolonged anger. Yet, we are incredibly bad at sleeping. According to the CDC, one in three Americans are sleep deprived — and that was before the pandemic made it worse.

Now, it’s obvious that apart from the whole host of benefits linked to sleep, not getting enough can accelerate aging. (I know — exactly the sort of thing you want to hear in the year of our lord 2021.)

According to a new study published in Sleep Health, sleepless nights can change your biological age. Your chronological age is the actual number of years you’ve been alive. Your biological age is how old your body seems, measured by biomarkers like proteins in your blood or telomere length.

The researchers studied 33 new mothers, ultimately finding that moms who slept less than seven hours a night within the first six months after birth were “three to seven years older” than those who slept seven hours or more.

It joins a handful of other studies that have also found a connection between sleep and aging. Here are four you should have in mind the next time you push back your bedtime.

1. Interrupted sleep influences biological age

University of California, Los Angeles researchers studied mothers during their pregnancy and the first year of their lives as new moms. They analyzed the mom’s DNA via blood samples — this is how they determined biological age.

Mothers who slept less than seven hours a night had an older biological age than their peers and had shorter telomeres in their white blood cells. (Telomeres are caps at the end of chromosomes — they naturally get shorter as we get older, but certain activities can prolong or quicken this process.)

“We found that with every hour of additional sleep, the mother’s biological age was younger,” first author Judith Carroll explained in a statement.

Critically, Carroll and colleagues emphasize that they’re not saying mothers are “permanently damaged” by this — they simply don’t know if the effects are long-lasting or not.

But it’s cause for more research: Generally, the greater the biological age, the greater the risk of disease and earlier death. It’s also a lesson for everyone: It’s not exactly the fact that these were mothers that caused the change; it’s that this is what happens to humans when they don’t get enough sleep.

2. Seven hours really does matter

In 2019, a study published in Nature revealed that people who slept fewer than five hours a night had significantly shorter telomeres than those who slept seven. Shorter telomeres are known to be a biomarker for accelerated aging.

These researchers based their results on an analysis of 482 people. At the time, co-author Weng Khong Lim told Inverse the findings drive “home the message that meeting NSF guidelines for sleep is important in order to avoid incurring health risks associated with insufficient sleep.” The National Sleep Foundation (NSF) recommends adults get seven to nine hours of sleep each night.

3. Sleep affects your cells

Another study co-authored by Carroll, this one published in 2016 in the journal Brain, Behavior, and Immunity, found sleep loss increased expression of DNA damage response in genes. This analysis was conducted on 29 adults between the ages of 61 and 86.

Ultimately, the study found one night of partial sleep deprivation promoted biological aging. This is thought to be because it damages the cell cycle process and increases susceptibility to senescence — the loss of a cell’s ability to divide and grow.

4. There’s a link between sleep, the gut, and death

In a 2020 study published in Cell, researchers argued that prolonged, severe sleep loss could be lethal. The reason for this is unknown, so the scientist examined sleep-restricted flies and mice.

Subsequently, they found that prior to death, the sleep-deprived flies experienced an accumulation of molecules in the gut called reactive oxygen species (ROS). Mice experience confirmed this finding too.

However, when flies were given compounds that neutralized and cleared the reactive oxygen species from the gut, they recovered and went on to live normal lifespans. While it might sound strange, these preliminary findings suggest some animals could perhaps survive without sleep — if this gut interference happens.

“We found that premature death could be prevented,” senior author Dragana Rogulja, an assistant professor at Harvard Medical School, explained in a statement.

“Each morning, we would all gather around to look at the flies, with disbelief to be honest. What we saw is that every time we could neutralize ROS in the gut, we could rescue the flies.”