So how much shut eye do we really need each night? New guidelines have been revised to indicate that 7 hours is probably about right for many adults. The guidelines (see left) also to emphasise that there is a range when it comes to sleep need. Some people get by on 6 hours just fine, and some need as many as 9 or even 10 hours.
It is helpful to think about sleep need in a similar manner to how we think about height, or shoe size, in that there is a large variation in what is 'normal' and healthy.
A University of California, San Diego psychiatry study of more than one million adults found that people who live the longest self-report sleeping for six to seven hours each night. To maximise your opportunity for sleep improvement, it is helpful to set aside any previous notions you might have about your sleep needs.
The National Sleep foundation recommends 6-10 hours for most adults, but settles on 7 hours as the magic number required by most.
There are exceptions, with some people functioning well on only 4 ours a night - Margaret Thatcher was a famous example of this 2% of the population.
There is also evidence that women need a little more sleep than men, possibly because they use more of their brain (eg multi tasking) during wakefulness.
More is not always better
There are drawbacks from sleeping more than our body requires, night after night, as this reduces sleep ‘pressure’ at bed-time, causing a longer time to fall asleep, followed by more fitful sleep overnight. Further, there is evidence that 7 hours sleep a night is associated with greatest longevity.
Sleep across the lifespan
Total sleep time reduces across the lifespan, with children needing more sleep than adults. The latest guidelines from the National Sleep Foundation have widened the recommend range of hours sleep per night - supporting that there is a range in sleep need across individual children. For example, the new guidelines for primary schoolers suggest 9-11hrs per night (was previously 10-11).
When looking at the figure above, look at both the recommended hours of sleep and also the 'may be appropriate' ranges. The ranges are quite large, reflecting that sleep needs can vary quite a bit from person to person.
Toddlers: 9.5 - 15.5 hours may be appropriate (including naps)
Preschoolers: 8.5 - 14 hours may be appropriate (including naps)
School age children: 7.5 - 12 hours may be appropriate
Teenagers: 7 - 11 hours may be appropriate
Adults: 6 - 10 hours may be appropriate
Older Adults: 5.5 - 9 hours may be appropriate
The take home message for adults is that sleeping consistently less than 6 hours is probably not enough, but you may not need 8. How you function during the day will help you decide if the sleep you are getting is right for you. If you have concerns about you sleep, speak with your GP or get in touch with Sleep Matters.