In the Nurses’ Health Study that followed 71,617 women for a decade, those who slept eight hours a night had the lowest risk of developing heart disease. But in another study that followed 84,794 nurses for up to 24 years, those who slept nine or more hours a night were twice as likely to develop Parkinson’s disease as those who averaged six hours or less.

Still, many more people, both lay and professional, worry more about too little sleep than an excess of shut-eye, and with good reason. Sleep-deprived people have more accidents and are more likely to fall asleep at inappropriate times, like at a play or concert or, most seriously, while driving.

Drowsy driving slows reaction time as much as drunken driving does. According to the National Highway Traffic Safety Administration, fatigue results in 100,000 auto crashes and 1,550 automotive deaths a year in the United States. Several automakers, including Subaru, Audi, Mercedes and Volvo, now offer drowsiness detection systems that monitor a car’s movements, such as lane deviations, and alert sleepy drivers to take a break.

Sleep deprivation was a factor in some of the biggest environmental disasters in recent decades, including the 1979 nuclear accident at Three Mile Island, the 1986 nuclear meltdown at Chernobyl and the 1989 Exxon Valdez oil spill in Alaska.

Although you might expect the opposite, several studies have shown that short sleepers tend to weigh more than those who sleep for longer periods, even though people expend more calories while awake than asleep. A study of 990 working adults in rural Iowa found that the less sleep they got on weeknights, the higher their body mass index tended to be.

A Canadian study of 240 children who ranged in age from 8 to 17 showed it was not helpful to try to make up for short weeknights by sleeping longer on the weekend. Fluctuating hours of sleep can affect appetite-regulating hormones in ways that prompt people to eat when they’re not hungry and eat past the point of satiation. The Wisconsin Sleep Cohort Study found that short sleepers had low levels of the appetite-suppressing hormone leptin, and higher levels of the hormone ghrelin, which signals people to eat more.

Furthermore, an attempt to make up for lost sleep on the weekend has been associated with eating in the absence of hunger or in response to fatigue, as well as being unduly tempted by the sight or smell of food. I can attest to a common tendency to eat more — especially snacks of questionable nutritional value — when staying up past what should have been a reasonable bedtime.

Experts offer a variety of tips for getting a better night’s sleep. Among them:

  • Avoid all sources of caffeine in the late afternoon and evening, as well as a big heavy meal close to bedtime.

  • Practice good sleep hygiene. Go to bed and get up at about the same time each day.

  • Do not use alcohol to help you unwind. Try a warm bath or meditation.

  • Reading before bed is great, as long as it’s not on a computer or tablet that emits sleep-inhibiting light.

  • If outside light impedes sleep, install light-blocking shades or curtains or use a sleep mask. If noise is a problem, use earplugs or a white-noise machine.

  • Consider cognitive behavioral therapy, which challenges underlying thoughts or behaviors that may be keeping you up at night.

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