How much sleep do people need?

Sleep is an essential part of our daily life cycle, but how much sleep do we really need for maximum health benefits?

Photo Credit: Alex Bramwell
By Michael Pollick

This question of how much sleep a person needs falls along two paths. There are ongoing debates over how much sleep is required for maximum physical health and how little sleep is required for mental acuity. Both sides of the sleep issue need to be considered before formulating a solid working answer.

Conventional wisdom suggests that an adult needs eight hours of quality sleep per night for maximum health benefits. Many sleep experts have now started to back away from this standard, attributing its enduring popularity to the work schedules of our agrarian ancestors. Back in the days of dusk to dawn workdays, sleep patterns were largely determined by the sun. People became conditioned to falling asleep shortly after dusk and awaken at the first signs of morning sunlight. It was believed that this circadian rhythm of 8 hours of sleep and 16 hours of wakefulness was the norm.

Modern tests in sleep laboratories have shown that the natural circadian rhythm of humans averaged 25 hours without the benefit of triggers such as light or dark. Years of conditioning by the 24 hour sun cycle have changed our sleep requirements accordingly. Infants and toddlers may require 11 to 12 hours of uninterrupted sleep per day, accompanied by a few hours of napping. Older children and teens may only require 9 or 10 hours of sleep, but rarely get more than 8 during the average schoolday. This sleep debt results in the extra long sleeping patterns of teenagers on weekends.

Many adults benefit from 7 or 8 hours of actual sleep, which may vary from the times they assign to it. Adults may lose an hour or so of quality sleeptime as they try to decompress from the day’s stressors. Sleep experts suggest that people who have difficulty falling asleep refrain from caffeinated drinks and television viewing at least an hour or two before bedtime. Beds should ideally be associated with sleep, so experts also suggest not having a television or other entertainment center in the bedroom. Many people find it helpful to delay going to bed until exhaustion sets in, whether it be right at the assigned bedtime or a few hours before or after.

Sleep is not a period of non-productive hibernation between activities. From the time we wake up, we cause damage to our bodies. Skin cells are damaged by wind or heat or cold. Muscles become torn as we walk or exercise. Our minds become filled with extraneous bits of information which have nowhere to go. Digestive systems work constantly to process the foods we ingest throughout the day. All of these vital systems need a chance to repair themselves, which means we need to stop moving for a few hours. While we sleep, our bodies can rebuild tissues, process new information and eliminate wastes. Not allowing time for our system to heal leads to increased chances of sickness and a lingering feeling of sleep deprivation.

Some sleep experts also debate the amount of sleep needed to restore mental acuity. This is a critical issue among health professionals and others who spend countless hours without sleep. These workers may have to make critical decisions during periods of extreme sleep deprivation. Experiments with sleep-deprived mice have show that a mouse who receives no sleep at all can actually die after three weeks, compared to the two or three year lifespan of a similar mouse allowed to sleep normally. Concerns over mental acuity have led to mandatory sleep periods for medical residents and others who work long shifts.

There is no single answer to the question of how much sleep is necessary. In general, if you sleep uninterrupted for a number of hours and awake refreshed, then you have probably had enough sleep. If you feel extremely lethargic upon waking and lose focus during a lecture or other routine activity, then you are most likely sleep-deprived. A regularly scheduled nap may restore some of the sleep debt, as well as changing your pre-sleep schedule to allow more time for sleep.