7 Convincing Reasons To Get A Good Night's Sleep

Seven -- that’s the average number of hours slept each night by women who scored highest on cognitive tests (reasoning, vocabulary, memory and more). When sleep decreased to six or fewer hours nightly, scores plummet -- especially in reasoning and vocabulary -- and the brain effectively aged by four to seven years, found a five-year study published in the journal SLEEP. While correlation isn’t causation, sleep has restorative properties -- and the habitual seven hours has also been linked with a lower dementia risk later in life.

Surplus sleep is more effective than painkillers -- a surprise discovery by researchers at the Sleep Disorders and Research Center at Henry Ford Hospital. When drowsy people were allowed to sleep for up to 10 hours, four nights in a row, they were 25 percent less sensitive to pain (more effective than 60 milligrams of codeine!) and more alert, compared with those who slept their normal hours. The lesson: While any sleep helps decrease pain sensitivity, an extra one to two hours for several nights before a surgery or procedure may steel you even more.

Cheat yourself of two or more hours of sleep each night this workweek and you may find yourself two pounds heavier by Saturday -- as volunteers did in a study at the University of Colorado at Boulder. Eating more is one explanation. The other is what you’ll eat: pasta, cake, bread -- anything high in carbs -- especially after dinner. Even a night or two of short sleep boosts the hormone ghrelin, which stimulates the appetite, and decreases leptin, which suppresses it.

One more reason to get at least seven hours nightly? The simple carbs you can't help but love -- soda, pasta, the deep-fried pretzel dog -- would be (well, not exactly healthy but) less harmful than when you’re sleep-deprived. Even one night of shortened sleep decreases our ability to clear glucose from the blood -- by up to 25 percent -- found researchers at Leiden University in the Netherlands. After six years of mild sleep deprivation, volunteers in a SUNY Buffalo study were three times likelier to have abnormal blood sugar levels -- on the slippery slope to diabetes.

Clock in your seven hours of shut-eye -- no less -- and avoid a striking 62 percent increase in breast cancer risk, finds an eight-year Japanese study of 24,000 women. The theory: Without adequate sleep, the light-sensitive pineal gland doesn’t secrete enough hormone-regulating melatonin. That’s a problem, because our bodies use melatonin to suppress the hormone estrogen -- which, unchecked, may stimulate (cancerous) breast cell division.

Look at something cute -- like bunnies and ice cream sundaes (or perhaps any guy in a baseball cap). If you have underslept, you may respond more positively than usual (even giddily), as sleepless volunteers did in an fMRI study at UC Berkeley and Harvard. Sleep deprivation spikes the hormone dopamine, which excites the brain’s reward-motivation-and-sex-drive-related pathways, and suppresses the “rational” prefrontal cortex. The result: risky, over-optimistic, impetuous decisions. (Mix sleepiness with alcohol and you’re also likelier to drink more than you otherwise would.)

We've all heard that a weekend of “catch-up” sleep can't compensate for getting six hours or less all week. (The bounce-back actually takes a week or two of extended sleep.) The good news (for those who can plan ahead) is that if we get the extended sleep up front -- 10 hours a night, every night -- it’ll protect us from subsequent short sleep. The Walter Reed Army Institute of Research found that a week’s investment (early to bed, late to rise) before a week of sleep deprivation adds up to longer-lasting alertness and a speedier recovery period.