This is Exactly How Much Sleep You Need

  • By Quentin Fottrell, Marketwatch
  • October 17, 2014

sleep time

How much sleep do you get every night? Studies show that most people try to muddle by on less than seven hours, but new research claims to have found the exact amount of time we need.

Men need 7.8 hours per night and women need 7.6 hours, according to a study that tracked 3,760 people over seven years and published in the September issue of the journal Sleep. They cross-referenced data on work absence due to illness from Finland’s Social Insurance Institution with sleep disturbances and sickness absence of the study’s participants, who were examined by physicians. After adjusting for age, education, working conditions, health behaviors and mental health, the scientists calculated the “optimal sleep duration.”

Sleep experts say the results are particularly relevant in the U.S., where 40 percent of people get less than seven hours of sleep a night, according to a 2013 Gallup poll. Americans, on average, had what’s now regarded as the optimal amount of sleep in the 1940s (7.9 hours per night), but that’s fallen to 6.8 hours in 2013. Americans aged 65 and older report getting the most sleep (67 percent get 7 or more hours per night) while only 54 percent of 18- to 29-year-olds and less than half of 18- to 29-year-olds report getting 7 or more hours.

The American Academy of Sleep Medicine recommends between 7 and 9 hours per night, but Nathaniel Watson, president of the American Board of Sleep Medicine, says people are getting less sleep in part because of their increasing reliance on technology. “We generally recommend that people have a period where they wind down before they go to sleep,” he says. “When people are interacting with technology, not only are they interrupting with that wind down period, but they’re being stimulated by blue wavelengths of light, which further makes sleeping difficult.”

What’s more, studies show that people overestimate the amount of time they sleep by around 45 minutes, says James Maas, former chairman of the Department of Psychology at Cornell University who is widely credited with coining the term “power nap”. “Sometimes, you’re going to toss and turn before you fall asleep,” he says. “It’s hard to know accurately the quantity without measuring brainwaves. You can be in bed for eight or nine hours and have a bad sleep.” Bad dreams don’t help, he adds. “Your blood pressure may go up. Nightmares can be exhausting, mentally and physically.”

People experiencing sleep insufficiency are more likely to suffer from chronic diseases such as hypertension, diabetes, depression, and obesity, plus cancer, increased mortality, and reduced quality of life, according to the Centers for Disease Control and Prevention. Simon Rego, director of psychology training at Montefiore Medical Center in New York City, says each person has a unique sleep requirement.

“A simple definition for sufficient sleep is a sleep duration that is followed by a spontaneous awakening and leaves the person feeling refreshed and alert for the day,” he says.

Quentin Fottrell is a personal finance reporter for MarketWatch based in New York. You can follow him on Twitter @quantanamo. This article originally appeared on and is reprinted by permission from, ©2014 Dow Jones & Co. Inc. All rights reserved.

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