The amount of sleep adults need has once again come under the spotlight, with a recent Wall Street Journal article suggesting seven hours sleep is better than eight hours and the American Academy of Sleep Medicine drawing up guidelines surrounding sleep need.
So, what should the guidelines say? Unfortunately, when it comes to the amount of sleep adults require there is not really a “one size fits all”. Sleep need can vary substantially between individuals.
Sleep is regulated by circadian and homeostatic processes, which interact to determine the timing and duration of sleep. The circadian process represents the change in sleep propensity over 24 hours, or our internal “body clock”. The homeostatic process represents the accumulation of sleep pressure during wakefulness and the dissipation of sleep pressure during sleep.
Both the circadian and homeostatic processes are influenced by internal factors, such as genes, and external factors, such as prior sleep history, exercise and illness. Individual variations in sleep timing and duration can be largely explained by these internal and external factors.
Individual Sleep Need
Genes are important in determining diurnal preference: whether we are “night owls” who prefer to stay up late at night, or “early birds” who prefer to get up early in the morning. Genes may also contribute to whether we are “short” or “long” sleepers.
But although genes form the foundation for sleep timing and duration, many external factors also affect sleep need.
Perhaps one of the more common causes affecting sleep duration relates to sleep history. Many adults, whether they know it or not, experience sleep restriction, often on a daily or weekly basis. Restricting sleep or going without sleep (pulling an “all-nighter”) increases sleep pressure.
This sleep pressure dissipates within sleep, so higher sleep pressure requires longer sleep duration. As such, following sleep loss, sleep need increases.
