7 hours (or more) of sleep Experts lower the bar slightly on sleep recommendation The latest findings on sleep

Registered Sleep Technician Lance Anderson prepares patient Mark Henrion for a sleep study at Summerville Sleep Center.

In the past two months, a flurry of studies on sleep have been published and presented. Here are some of them:

Most, but not all, physical activities helps you sleep better

Certain types of physical activities help you sleep better, while others might leave you tossing and turning, a new study finds.

Researchers looked at data from a survey of more than 429,000 American adults. They found that activities such as walking, bicycling, running, weight-lifting, aerobics/calisthenics, gardening, yoga/Pilates and golfing were all linked to better odds of a good night’s slumber.

However, people who got physical activity from household chores and child care had a greater risk of poor sleep, according to the study.

Results of the study were presented earlier this month at the annual meeting of the Associated Professional Sleep Societies in Seattle. Findings presented at meetings are generally viewed as preliminary until they’ve been published in a peer-reviewed journal.

The results of this study were surprising, according to study leader Michael Grandner, a psychiatry instructor at the Center for Sleep and Circadian Neurobiology at the University of Pennsylvania in Philadelphia.

“Not only does this study show that those who get exercise simply by walking are more likely to have better sleep habits, but these effects are even stronger for more purposeful activities, such as running and yoga, and even gardening and golf,” Grandner said in a university news release.

“It was also interesting that people who receive most of their activity from housework and child care were more likely to experience insufficient sleep. We know that home and work demands are some of the main reasons people lose sleep,” Grandner added.

Study found insomniacs who didn’t eat after 10 p.m. were more alert

Concentration and attention problems caused by sleep deprivation might be eased by eating less late at night, according to a new study from the University of Pennsylvania in Philadelphia that was presented this month at the annual meeting of the Associated Professional Sleep Societies in Seattle.

The research included 44 volunteers, age 21 to 50, who were given unlimited access to food and drink during the day for three days but were only allowed to sleep four hours a night.

“Adults consume approximately 500 additional calories during late-night hours when they are sleep-restricted,” senior author David Dinges, director of the unit for experimental psychiatry and chief of the division of sleep and chronobiology at the university.

On the fourth night, about half of the participants continued to have unlimited access to food and drink. The other half were restricted to water from 10 p.m. until they went to sleep at 4 a.m.

At 2 a.m. on each of the four nights, the participants underwent tests to measure their memory, thinking skills, sleepiness, stress level and mood.

On the fourth night of sleep restriction, those who fasted had better reaction times and fewer attention lapses than those who ate, the findings showed. Also on the fourth night, those who ate had much slower reaction times and more attention lapses compared to the first three nights. The people who fasted didn’t show a decrease in performance, the investigators found.

In another study to be presented at the meeting, the same team of researchers found that adults with chronic lack of sleep have a reduced metabolism. The researchers suggested that people may need to compensate for this loss of calorie-burning power by increasing their physical activity levels or reducing their calorie intake to prevent weight gain after sleep deprivation.

This study included 36 healthy adults aged 21 to 50. Their resting metabolic rates — how much energy their bodies use when relaxed — was measured after normal nights of sleep, and after five nights of sleeping just four hours a night.

Resting metabolism decreased after sleep deprivation, the study found.

Insomniacs may be more sensitive to pain

People with insomnia or poor sleep quality may be less tolerant of pain, new research from Norway suggests.

The researchers also noted that people with insomnia who also suffer from chronic pain have an even lower threshold for physical discomfort. The study was not designed to show a cause-and-effect relationship.

The study, led by Borge Sivertsen of the Norwegian Institute of Public Health in Bergen, involved more than 10,000 adults. The study participants all underwent a standard test of pain sensitivity by dunking their hands in a bath of cold water for 106 seconds.

The volunteers were asked about their sleep quality. Specifically, they were questioned about insomnia, how long they slept and how long it took them to fall asleep. The researchers also took into account other factors that might affect pain tolerance, such as recurring pain, depression and anxiety.

They found that nearly one-third of participants were able to keep their hand in the cold water for the entire test.

Forty-two percent of people with insomnia pulled their hand out before the test ended, compared to 31 percent of those without this sleep disorder, the study published in the journal PAIN revealed.

Poor sleep and breast cancer

Breast cancer patients who had poor sleep and frequent snoring before their cancer diagnosis appear to have lower survival rates, a new study published in the journal Sleep finds.

The study, which was not designed to prove cause-and-effect, included more than 18,000 cancer patients whose progress was tracked in the Women’s Health Initiative study.

Researchers led by Amanda Phipps, an assistant professor of epidemiology at the University of Washington in Seattle, found that women who slept 6 hours or less per night and were frequent snorers had more than twice the odds of a poor prognosis compared to women with neither of those factors.

A similar finding was seen for women with lung cancer, although the effect was not as large as was seen in women with breast cancer, the study authors said.

“Our results suggest that sleep duration is important for breast cancer survival, particularly in women who snore,” Phipps said in a journal news release.

Link between sleep and young children’s mental health

Researchers at the Norwegian University of Science and Technology looked at sleep patterns and the mental health of 1,000 children starting when they were toddlers.

They found that those with sleep disorders at age 4 were at increased risk for mental health problems such as anxiety and depression at age 6. They also discovered that children with mental health problems at age 4 were at increased risk for sleep disorders at age 6.

Due to the study’s design, however, it wasn’t possible for the researchers to prove that sleep problems caused mental health issues or vice versa; the researchers could only show an association between these factors.

Insomnia was the most common type of sleep disorder. Insomnia was diagnosed in nearly 17 percent of the children at age 4 and in 43 percent of them at age 6. Insomnia increased the risk of anxiety, depression and attention-deficit/hyperactivity disorder at age 4 and the risk of behavioral problems at age 6, the study authors said.

Source: Healthday/Medline Plus, National Institutes of Health.