We are often told we need to aim for 8 hours sleep per night. But where does this recommendation come from? And what is the science behind why we need to sleep? Everyone has that one friend who likes to tell you they regularly get 5 hours sleep a night and “feel fine” or brag that it “never does me any harm”. So let's consider if it actually does.
Many studies have been carried out looking at how often diseases occur in groups of adults across a population. Short sleepers (4-5 hours per night) have been shown to be more likely to develop diseases and have a shorter lifespan. This likelihood of developing diseases decreases as sleep time increases, with the lowest levels of disease being shown in participants who regularly get around 8 hours sleep per night.
Interestingly, the likelihood of developing disease increases in people regularly getting 9-10 hours per night. This fact could be accounted for due to lifestyle variable of those regularly getting that much sleep; It could be indicative of a more sedentary lifestyle perhaps lacking activity which as we know is another risk factor for potential disease. Children and adolescents have different sleep requirements and results from studies such as the above cannot be extrapolated to advise these populations.
Chronic sleep deprivation has been linked in numerous research papers to poor health outcomes. These health outcomes include both psychological and physiological disorders. A review of over 150 studies recently demonstrated short sleep time to be significantly associated with diabetes, cardiovascular disease and obesity.
In terms of psychological issues, regular lack of sleep lowers cognitive functioning and has been linked to the development of dementia in later life. During waking hours, toxins build up in our brains - sleep is vital to remove these toxins.
In the UK, our increasing rates of obesity is probably not helped by the fact we are a nation of poor sleepers. Many people simply don't see the value in prioritising sleep over lifestyle factors such as work or socialising. A lack of sleep is associated with the production of the hormone ghrelin - which is responsible for making us feel hungry. Chronic tiredness therefore could lead to overeating, which in turn contributes to rising obesity levels across the country.
Sleep problems vary considerably by age and gender, with women reporting the most difficulty in getting enough sleep than men. As adults, women tend to report more sleep deprivation than men, which could be due to the fact women are traditionally more likely to be up with young children during the night. This gender gap then decreases in later life.
Caffeine and alcohol are two factors which significantly affect our sleep. With us being a nation of coffee lovers, consumption of too much caffeine could be a reason why some of us aren't getting enough sleep per night. Even if you are diligent with the hours you spend in bed and aim for the golden 8 hours, if you’ve consumed excess caffeine during the day this could be affecting sleep quality and ability to go to sleep in the first place. Consider limiting your caffeine to the mornings only, giving your body a chance to metabolise it prior to bedtime and stop it affecting your sleep.