Should you judge sleep by quantity or quality?

When it comes to getting a good night’s sleep, there are a lot of things we still don’t know.

Yes, duration of sleep is important, but we shouldn’t get too hung up on whether we got six hours or eight hours. The recommended amount is seven to seven and a half hours a night for an adult, but the minimum duration for a good night’s sleep should be judged by how you feel and act during the day. If you are feeling sleepy and you can’t do your job, then you are probably not getting enough sleep. I think we also need to be more flexible about sleep habits. So for example, a block of sleep through the night is great but a short nap in the afternoon can also add to overall sleep quality. It depends a bit on the individual.

Most individuals who sleep for over six hours each night without interruption will have four full sleep cycles. There are two stages of a typical sleep cycle which takes around 90 minutes – non Rapid Eye Movement sleep, which can be subdivided into light and deep sleep, and Rapid Eye Movement sleep. As we age, the time we spent in deep sleep reduces. This starts to happen from the late teens and continues throughout life. Men lose a little bit more deep sleep than women over time. Someone who is in their 70s will only get around half the deep sleep time of someone in their 20s. Deep sleep is linked to restfulness and certain aspects of cognition, such as how quickly you can do certain tasks.

We don’t lose REM sleep time as we age, which may be important for emotional processing as well as helping the brain store away data.

Quality of sleep can be affected by what we eat and drink. Alcohol and caffeine do increase restlessness and promote early waking.

External stimuli such as noise and light can also interrupt sleep.

Obesity is another factor which can severely impact on quality of sleep. Many sufferers of sleep apnoea, when someone may stop breathing 100s of times each night causing sudden arousal, are overweight or obese. Fat cells also produce cytokines which cause sleepiness during the day, leading to difficulties falling asleep at night. Losing weight can ease these problems.
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