A Bit of Exercise May Protect Memory After a Bad Night's Sleep, Study Finds

A restless night does more than make for an irritable day at the office. It can erode recall and make it harder to retain information or learn new skills. Researchers from Concordia University in Canada tested whether physical activity, already known to offset some effects of sleep loss, could also protect memory from the effects of a bad night's sleep.

The study randomly divided 88 healthy young volunteers into one of four groups. Half received a typical amount of sleep, while the other half were permitted just 4.5 hours of the recommended 8.5 hours of nightly sleep. Each group was then split again, with half doing 30 minutes of moderate-intensity cycling and half sitting in a chair for 40 minutes. Before bed, participants played an image-matching memory game, judging whether faces shown to them were part of a set they had seen earlier or were new. A similar test was repeated the next day.

Volunteers who slept soundly performed best on the memory game the following day, while those who did not get enough sleep were significantly slower to answer. Exercise appeared to help: among the sleep-deprived group, those who had cycled showed far less delay in recall than those who had simply sat before bed. The researchers said the study adds evidence for moderate physical activity's effect on a sleep-deprived brain, while acknowledging limitations, including that testing the same participants under different conditions would help rule out confounding factors.

Deep sleep, the slow-wave stage the brain enters during rest, is vital for memory retention and is the kind of sleep people miss when they stay up late. Poor sleep can also elevate inflammation, interfere with metabolism, and raise the risk of chronic conditions such as heart disease and dementia. The research was published in the journal Sleep.