How much sleep is enough?

Many people don't assess how much sleep they need to function at their best; they just know they don't get enough. Each person's sleep requirement is different. Some people find that they only need 5-6 hours of sleep, while others need 10-11 hours for optimal performance. The average adult functions best with7-8 hours of sleep a night; however, it is important to consider
how much sleep you need on an individual basis.

The number of hours needed to sleep is a matter of "circadian rhythm," or the biological clock function which regulates our sleep-wake cycles.

Humans are evolved to be "diurnal" creatures, as opposed to nocturnal, that is we are hard-wired to operate optimally in the daytime; sleeping at night.

As newborns, we are essentially neither diurnal or nocturnal, having sleep-wake cycles which are frequent and evenly spaced during any 24-hour period; sleeping for 3-4 hours, waking for 1-2 hours, around the clock.

During the first year, this pattern progresses toward consolidation of the sleep period, trending toward increased nocturnal sleep and daytime wakefulness. At one year the infant typically sleeps about 10 hours from around 7 pm until about 5 am, with a couple of naps in the early and late afternoon, respectively.

By age 4-5, the child has lengthened the nocturnal period to about 11-12 hours with one nap in the afternoon.

At age 10, time of sleep onset is somewhat delayed to 8 or 9 pm, and sleep lasts until 6 or 7 am; the nap disappearing.

For most adults, 7 to 8 hours a night appears to be the best amount of sleep, although the amount ranges from 5 hours to 10 hours of sleep each day depending on the individual. It should be noted that a recent research study conducted by Boston University School of Medicine found that study participants that reported sleeping less than 6 hours or more than 9 hours a day had an increased incidence of diabetes, compared to those who slept 7-8 hours

Senior adults were long considered to have further shortened sleep requirements, but it is now thought that this is only because they tend to get less sleep due to increasing intrinsic sleep disturbance, such as sleep apnea, or musculoskeletal pain, which may interrupt or truncate the sleep interval.

The need to nap is not a clear-cut issue, as some cultures agree that a "siesta" in the afternoon is "natural," and people of all ages in those cultures normally take a mid-day snooze.

Sleep lab data suggest strongly that if adults get 8.1 hours of undisturbed sleep in a 24 hour day, that a nap will not be needed. This varies based upon the quality of sleep obtained, and other factors such as state of general health, levels of stress, or fatigue due to prolonged exertion.