How Much Sleep Do We Need After 40 and After 60?

This difference between the need for sleep and the ability to produce it is key. If after sixty you sleep six hours and feel well during the day, there is no reason to worry. If you sleep the same amount but are sleepy, sluggish and find it hard to concentrate by day, short sleep may be a sign of insufficient restoration rather than of lower need. That is why the recommendations are a reference point, not a rigid limit.

In this article we focus on what happens to sleep after forty and after sixty, and how to interpret the frequently cited studies showing that both too short and too long sleep are associated with higher mortality. General information about the role of sleep in aging can be found in our entry on sleep, aging and longevity.

The National Sleep Foundation convened a multidisciplinary expert panel that evaluated the current scientific evidence and, through a formal voting process using the RAND/UCLA method, formulated recommendations for nine age groups. For young adults and adults the recommended range is 7-9 hours a day, and for older adults 7-8 hours. For each group the panel designated ranges as 'recommended', 'may be appropriate' and 'not recommended', which underlines that these are frames, not a single number for everyone.

It is worth remembering that besides the National Sleep Foundation, American sleep societies have also published their own recommendations for adults, and all these documents fall within similar limits. None of them stems from a study that would show a strict 'optimal' number of hours: they are consensus statements based mainly on observational data, which we discuss below.

A meta-analysis of objective sleep studies (polysomnography or actigraphy) in healthy people found that in adults, total sleep time, sleep efficiency, the percentage of slow-wave (deep) sleep, the percentage of REM sleep and REM latency all decrease with age. At the same time, sleep latency, the percentage of light sleep (stages 1 and 2) and wake after sleep onset increase. In practice this means shallower and more interrupted sleep, which for the same number of hours in bed gives less restoration.

The last sentence of this summary is particularly important: a large part of the 'normal' changes in sleep with age may result from accompanying conditions that become more common after forty, such as apnea, pain, nocturia, mood disorders and medications. This is a prompt not to accept worsening sleep as inevitable, but to check whether its cause can be found and treated. We write about sleep stages in more detail in the sleep entry.

After sixty the changes described above typically deepen, and a shift of the body clock is added. An analysis of time-use diary data from more than 53,000 people in the US found that the average chronotype shifts later during adolescence, peaks in 'lateness' at about age 19, and then shifts systematically earlier. Men are usually later chronotypes than women before age 40, and earlier ones after forty.

In practice many people over sixty fall asleep early in the evening and wake at dawn. It is not a disorder if it fits your lifestyle and causes no problems, but it can be awkward when you want to stay up longer in the evening. Daylight exposure during the day, movement, regular sleep times and limiting late-afternoon naps help. We describe the topic in detail in the chronotype entry.

The most frequently cited data on sleep duration come from meta-analyses of prospective cohort studies. In one of them, covering 16 studies (27 independent cohort samples), more than 1.38 million participants and 112,566 deaths, both short and long sleep were associated with a higher risk of death: for short sleep the relative risk was 1.12 (95% CI 1.06-1.18) and for long sleep 1.30 (95% CI 1.22-1.38). A graph of such a relationship has the shape of the letter U.

One should not conclude from this that 'too much sleep shortens life'. Observational studies with self-reported sleep do not settle the direction of the relationship: seriously ill people, people with depression, undetected apnea or early neurodegenerative disease may stay in bed longer and at the same time have a higher risk of death from the illness itself (so-called reverse causation). Sleep time measured by questionnaire is also often overestimated, because people report time in bed. The result more likely means that extreme sleep durations can be a marker of a health problem, not that sleep should be measured by the clock.

If you want to find out how much sleep you actually need, during a few days of holiday you can go to bed at a fixed time and wake without an alarm; after an initial period of 'catching up', sleep length usually stabilises. Treat this result as approximate: it is not a clinical test, and the outcome depends on earlier sleep debt and circumstances. Details of sleep hygiene are collected in separate materials in the knowledge base.

After forty and sixty there is no reason to assume that less sleep is enough, but there is reason to make sure that sleep is of the best possible quality. Aim for the range recommended for your age, judge yourself by how you function during the day, and treat persistent worsening of sleep as a prompt to check for apnea, nocturia, pain, mood and medications. Mortality statistics should not be a source of anxiety about a 'wrong' number of hours; their practical lesson is that an extreme sleep time is worth discussing with a doctor, not measuring.