How Sleep Loss May Affect Brain Age and Healthy Aging

What If I Don’t Get Enough Sleep?

You may have seen this line before.

“I’m twenty years old, with the stamina of someone in their fifties, the lower back of someone in their sixties, the neck of someone in their seventies, and the emotional regulation of a ten-year-old.”

The line is a joke about one’s own physical and mental condition, but it rests on an implicit rule: aging measured by the passage of time may differ from aging reflected in physiological indicators. In other words, people have a rough idea of what physical condition to expect at each age; otherwise, describing a bad back as “the back of someone in their sixties” would make no sense.

The brain can reflect this kind of age mismatch as well.

Using age-related patterns in physiological data such as the brain’s gray matter, white matter, and cerebrospinal fluid, scientists constructed a model of brain aging. They then set out to estimate participants’ brain age under different conditions in order to assess the effects of sleep.

All participants first had one night of adaptation sleep, followed by two nights of baseline sleep—from 11:00 p.m. to 7:00 a.m., or from midnight to 8:00 a.m.—to place everyone’s initial sleep condition on as similar a footing as possible.

Participants in the control group continued to receive eight hours of sleep each night. Those in the experimental group underwent chronic sleep deprivation, with only five hours in bed for five consecutive nights, either from 2:00 to 7:00 a.m. or from 3:00 to 8:00 a.m.

After that, all participants underwent 38 hours of total sleep deprivation following an initial eight-hour night of recovery sleep, which ran from 11:00 p.m. to 7:00 a.m. the next day or from midnight to 8:00 a.m. the next day. The sleep-deprivation period was followed by a ten-hour night of recovery sleep.

MRI data were collected after the baseline phase, after five days of chronic sleep deprivation with five hours in bed per night, after the first recovery sleep, and after total sleep deprivation. The researchers then measured differences between the groups and across the various stages.

The results showed that after total sleep deprivation—38 hours awake—participants’ estimated brain age was significantly higher than it had been at baseline or after the first recovery sleep. The finding was confirmed in different groups of participants, demonstrating that an increase in brain age caused by acute total sleep deprivation is a generally occurring phenomenon.

The good news is that ten hours of recovery sleep helped return brain age to its previous level.

Unlike total sleep deprivation, chronic sleep deprivation produced no significant change in brain age compared with baseline.

So the feeling that your brain has “crashed” after too little sleep, like the experience described earlier, is closely connected to an increase in brain age.

All right, so even if a brief lack of sleep makes my brain crash, it eventually recovers. Does that mean I can stay up whenever I like?

Of course not!

So Does It Matter Whether We Sleep?

We know that aging causes the brain’s structure to deteriorate, thereby affecting cognitive performance and everyday life. Yet some people seem to experience cognitive decline more slowly than others.

Imagine us in old age: while the rest of us are fumbling to remember a familiar name—“Ma... what was it again? Oh, Sun Honglei”—someone else can still recite the key concepts of introductory psychology without missing a beat. We would surely think, “Well, that person’s mind is still working remarkably well!”

What, then, might help us move closer to becoming “the person whose mind still works remarkably well”?

Existing evidence indicates that sleep quality is one of the factors influencing the changes in brain structure that underlie cognitive decline.

Ramduny and colleagues (2022) found that poor sleep quality and insufficient sleep were significantly associated with accelerated brain aging. Several forms of impaired sleep—including short sleep duration, problems involving sleep latency, poor sleep efficiency, and sleep disturbances—were positively correlated with the gap between brain age and chronological age.

More specifically, older adults with these kinds of sleep problems had brains estimated to be about two years older than their actual age, indicating accelerated aging.

Some readers may be thinking: it is only two years—what difference could that possibly make?

It does. It really does.

Estimates of the brain-age gap are increasingly being used as markers of brain health, helping researchers quantify the risk of brain degeneration and predict the severity of conditions ranging from mild cognitive impairment to dementia. Studies have also found that this gap can help predict the course of cognitive change in older adults without dementia and identify lifestyle factors associated with maintaining a younger brain.

Sleep is an essential part of quality of life.

You may have heard older people around you say that they wake very early because they cannot sleep, only to doze off again during the day.

If unhealthy sleep contributes to aging, and aging in turn further reduces sleep quality, do the two start lifting each other upward like someone trying to fly by stepping on one foot with the other, trapping us in a vicious cycle?

Closing Thoughts

The harms of staying up late have been discussed for years, and there is no shortage of methods intended to help people put down whatever they are doing and go to bed earlier.

People often joke, “Staying up late extends the younger part of your life and only takes years away from your old age. What a bargain.”

But the studies discussed above offer a different way to see it:

We are not extending the life we have now; during the night, we are moving closer to old age.