How much sleep do I really need?

DEAR DOCTOR K:

Between my young kids and a full-time job, I’m lucky if I manage five hours of sleep per night. My husband says I’m running on empty. How much sleep do I really need?

DEAR READER:

You’re not alone. According to the Centers for Disease Control and Prevention, the percentage of adults sleeping fewer than six hours per night has increased by 31 percent since 1985. I spoke to my colleague Dr. Stuart Quan, professor of sleep medicine at Harvard Medical School. He noted the many negative consequences of insufficient sleep.

Even occasional sleep deficiency makes a person more irritable and depressed. It slows reaction times and negatively affects mental and physical performance. In fact, 18 hours of continuous wakefulness has the same adverse effect on reaction time as being legally drunk. Adequate sleep is also needed for optimal learning and memory; staying awake all night impairs the learning of new information.

Being chronically sleep-deprived exacts a toll as well. One and a half weeks of just six hours’ sleep per night can have the same impact as staying awake for 24 hours straight.

Inadequate sleep also negatively affects your health. People who have sleep deficiency are at higher risk for developing high blood pressure, heart disease, diabetes and earlier death. In addition, inadequate sleep leads to increased hunger and a greater tendency for weight gain.

So how much sleep do you need? The American Academy of Sleep Medicine and the Sleep Research Society recommend that adults get at least seven hours of sleep a night for optimal health. Getting fewer than six hours of sleep, they note, is associated with worse health outcomes. (There is not enough evidence to say whether getting between six and seven hours of sleep a night is bad for health.)

Why does sleep deficiency impair the functioning of the brain? We don’t know for sure. Recent scientific studies have revealed a surprising possibility, one I’ve mentioned in this column previously.

The cells of the brain, like cells throughout the body, produce waste material. This waste needs to be removed from the brain, and then eliminated from the body. These recent studies have found that the brain may be much better at flushing out the waste when it is sleeping. If the brain needs seven to eight hours of flushing every night, but it gets only five to six hours, the waste could accumulate.

It’s not easy to get more sleep in today’s 24-hour society. You’ll need to make a real effort to make better lifestyle choices. For example, choose to go to bed earlier in the evening instead of staying up to watch TV.

Also, make sure you’re not doing anything to sabotage the time you do spend in bed. Exercise regularly early in the day, avoid caffeine and alcohol close to bedtime, and keep your bedroom cool. By doing so, you’ll boost the chances that the time you do spend in bed won’t be spent tossing and turning.