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We are always being told we should get 7 – 8 hours sleep a night. At night. But how many of us can manage that? And what about people who work at night? And babies?

What are sleep rhythms?

Sleep rhythms are also called circadian rhythms or circadian sleep cycles. Each 24 hour cycle regulated sleeping and waking and stages of sleep. However, although regulated by biological processes and brain chemicals, modern life interferes with natural circadian rhythms in humans. We don’t necessarily wake at dawn, and few, in any of us, retire for the night at sundown. (We have, quite literally, left that ‘to the birds’.)

Individual sleep-wake cycles

Our individual circadian clocks adapt to our lives and schedules. A variety of demands can impact our sleep cycle – from children to stress, getting up earlier to beat the traffic, to working night shifts.
These demands can permanently alter our sleep rhythms over time.

1. Adapted sleep rhythms

Some people are born ‘night-owls’, but some of us become night-owls – from habits, interruptions, or necessity. Our adjusted sleep rhythms help us get at least some of the benefits of sleep – without which we cannot survive or remain healthy in the long term.

2. Genetic differences in circadian rhythms

‘Night Owl’ vs ‘Morning Person’: yes, some people just don’t need to sleep as much as others, and some naturally gravitate toward late nights while others are naturally early to bed and early to rise.

Natural circadian cycle changes: age and sleep rhythms

  • Babies and teenagers need the most sleep. However, babies also need to eat often. Hence, their sleep rhythms are very different to those of teenagers.
  • Older adults and the aged need the least sleep. There is less of a biological imperative to sleep as you get older. Most 80 years old will only sleep 2 – 3 hours.

Sleep rhythms differ between individuals, the sexes, due to genes, age and environmental factors. But 7 – 8 hours sleep at night is still good advice for most adults with ‘standard sleep rhythms.’