Although the dangers of too little sleep are widely known, new research suggests that people who sleep too much may also suffer the consequences.

Specifically, investigators at the University of California in San Diego found that people who clock up 9 or 10 hours each weeknight appear to have more trouble falling and staying asleep, as well as a host of other sleep problems, than people who sleep 8 hours a night.

People who slept only 7 hours each night also said they had more trouble falling asleep and feeling refreshed after a night's sleep than 8-hour sleepers.

These findings, reported in the journal Psychosomatic Medicine, demonstrate that people who want to get a good night's rest may not need to set aside more than 8 hours a night, study author Dr. Daniel Kripke told Reuters Health.

He added that "it might be a good idea" for people who sleep more than 8 or 8 1/2 hours each night to consider reducing the amount of time they spend in bed, but cautioned that more research is needed to confirm this.

Previous studies have shown the potential dangers of chronic shortages of sleep-- for instance, one report demonstrated that people who habitually sleep less than 7 hours each night have a higher risk of dying within a fixed period than people who sleep more.

For the current report, Kripke and lead author Michael Grandner reviewed the responses of 1004 adults to sleep questionnaires, in which participants indicated how much they slept during the week - excluding naps - and whether they experienced any sleep problems.

Sleep problems included waking in the middle of the night, arising early in the morning and being unable to fall back to sleep, and having fatigue interfere with day-to-day functioning.

Kripke and Grandner found that people who slept between 9 and 10 hours each night were more likely to report experiencing each sleep problem than people who slept 8 hours.

In an interview, Kripke noted that long sleepers may struggle to get rest at night simply because they spend too much time in bed. As evidence, he added that one way to help insomnia is to spend less time in bed.

"It stands to reason that if a person spends too long a time in bed, then they'll spend a higher percentage of time awake," he said.

Alternatively, Kripke suggested that there may be a link between long sleeping and depression, noting that people who are depressed often temporarily feel better after skipping a night of sleep.

"It might be that depression is causing the long sleep, it might be that the long sleep is causing the depression," Kripke said.

Source: China Daily/Agencies