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The glymphatic system is the brain's "waste management" system. It carries fresh fluid into the brain, mixes the fresh fluid with waste-filled fluid surrounding brain cells, and flushes the mix out of the brain and into the blood.

People who ate healthy plant-based foods had a 10% reduction in stroke risk, compared with people who ate unhealthy plant-based foods, according to a Harvard study published online March 10, 2021, by the journal Neurology.

Although it has been known for some time that individuals with dementia frequently have poor, fragmented sleep, two new studies suggest that if you don't get enough sleep in midlife, you are at increased risk for dementia later in life.

Research we're watching

Urban legends have linked full moons to everything from werewolves to erratic behavior, but a new study connects them to something else � sleep loss. A Jan. 27, 2021, study in Science Advances found that people fell asleep later and slept for less time over all in the three to five days leading up to a full moon. The effect was even more pronounced in areas where people had less access to artificial light.

To come to their conclusions, researchers studied people in three communities in Argentina: one on the outskirts of a city, a small rural settlement with limited access to electricity, and a group of people in a remote area who had no access to electric light. The study authors also analyzed the sleep of 464 University of Washington students who took part in a sleep study. All participants wore sleep-tracking devices for at least one week and in some cases up to two months. The researchers compared their sleep patterns to the moon phases. Individuals took from 30 to 80 minutes longer to fall asleep during the lead-up to the full moon, and people lost anywhere from 20 minutes to 90 minutes of total sleep on those nights. The researchers said it's possible that the full moon made people more active at night, which is why sleep differences were more pronounced in communities with less access to electricity. Artificial light, they said, might produce a similar effect.

In the journals

Afternoon naps can recharge a weary body; now research has found they also may boost cognitive function. An observational study published online Jan. 25, 2021, by General Psychiatry looked at 2,214 healthy people ages 60 and older in China, where afternoon naps are common. The participants were asked about whether they napped at least five minutes after lunch. Two-thirds took naps, and the others did not.

Everyone then underwent testing to measure various mental skills, such as memory, naming, attention, calculation, and orientation. The researchers then obtained more specifics about their napping habits, including how long they napped and how often per week.