Sleep Archive

Naps can be healthy for adults who need to catch up on sleep or work odd hours, but they can also make it more difficult to sleep at night and be a sign of a sleep disorder. Naps should be short and limited to the early afternoon to prevent them from interfering with nighttime sleep. People who have the urge to nap daily should consider whether they need to improve their nighttime sleep habits.

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.

Whether you're an exercise novice or a gym regular, these tips can help you get the most out of your workout.

When it comes to exercise, timing is everything — but not in the way we normally think about timing. What matters most is making the time to exercise regularly, not when it happens. That said, your personal experience and specific goals may influence what workout schedule works best for you.

"If you're just starting a physical activity routine, any time that you feel motivated and energized enough to exercise is the best time for you," says Dr. Beth Frates, clinical assistant professor of physical medicine and rehabilitation at Harvard Medical School. For some people, that's in the morning; for others, the afternoon works better. But if you can work out with a friend, choose a time that works best for both of you, she suggests. Teaming up with an exercise buddy is more enjoyable, and you can hold each other accountable.

News briefs

A little afternoon snooze can help you feel more rested — and it might do you good in other ways, too. A small study from China published online Jan. 25, 2021, by General Psychiatry suggests that afternoon naps (between five minutes and two hours long) may be good for your memory and thinking skills. Researchers put more than 2,200 older adults through a series of health screenings that included blood tests and cognitive assessments, and also asked participants whether and how often they napped. About 1,500 of the participants were nappers. Compared with people who didn't nap, the nappers performed better on cognitive tests, scoring better on location awareness, verbal fluency, and memory. The study was observational, so it can't prove that napping caused the better cognitive test results. Previous studies have shown that afternoon nap benefits decline as age and nap duration increase. Short, frequent naps (less than 30 minutes, four times per week) have been associated with reduced risks for developing Alzheimer's disease. In contrast, people who take long naps (two hours or longer) appear to have worse cognitive function, although it is unclear what is cause and what is effect.

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