For this study, researchers wanted to assess the relationships between brain age and sleep deprivation. They recruited 134 people with a mean age of 25 to undergo different sleep conditions, with some going through total sleep deprivation, and others only partial.

The study authors define total sleep deprivation as over 24 hours of prolonged wakefulness. The partial sleep deprivation groups, meanwhile, slept for three or five hours a night.

Following the night of sleep (or lack thereof), participants had MRIs to look at their brains, where the study authors observed that those in the total sleep deprivation group showed an increased brain age by one to two years compared to their baseline MRIs.

The same effects were not observed in the partial sleep deprivation groups, which is reassuring if you’re prone to missing a few hours of sleep here and there. Plus, those participants in the total sleep deprivation group were able to get their brains back to baseline age once they got a full night of sleep.

“Together,” the study authors say, “the convergent findings indicate that acute total sleep loss changes brain morphology in an aging-like direction in young participants and that these changes are reversible by recovery sleep.”