Babies and teenagers seem to spend most of their time asleep, while seniors are up at the crack of dawn. As we age, our need decreases, but we all need to rest and recover. Most adults average eight hours a night – some a little more, some a little less – but the general consensus is that eight hours is optimum for keeping us healthy.
A third of our lives are spent asleep. Theories suggest this long stretch of slumber helps to process and file information our brain has received during the day, while repairing and rebalancing the body both mentally and physically.
"Sleep is an active period where a lot of processing, restoration, healing and strengthening occurs. Research has shown that sleep influences all of the body's major physiological systems, including our immune system and also impacts on our mental health, weight and overall quality of life," explains Maryanne Taylor, founder and sleep consultant at The Sleep Works.
"Sleep helps us to consolidate our memories. Our brains process a huge amount of information each day and while we sleep, parts of the information are transferred from short-term to long-term memory. We require a long period of sleep to restore and rejuvenate, grow muscle and repair tissue in order to maintain optimum health."
Sleep helps us maintain the function of our immune system, says Joanne Rodda, consultant psychiatrist at Re:Cognition Health: "When we have an infection, one of the things our body does is release chemicals that promote sleep. There is some evidence to suggest that people who respond to infection by sleeping more may have better outcomes from their illness, and sleep deprivation has been clearly shown to have negative effects on the immune system. Quite how sleep helps our immune system to function is not yet known."
More than half of us often or sometimes have trouble sleeping, and 10% of us always have problems with sleep or experience insomnia a recent YouGov poll carried out on behalf of AXA PPP Healthcare revealed. Relationships or family troubles are blamed by 44% of people, while 45% of adults surveyed said their work or career had a negative effect on sleeping patterns.
So what happens when we don't get enough sleep? The penalties are incremental, and will get worse until something changes; an occasional bad night might mean you are irritable, while several can affect your concentration and mood but it is the accumulation over weeks and months that can lead to more serious health complications such as high blood pressure, obesity and diabetes.
After one night
You might find you have a short temper, can't focus and you feel tired and irritable. You may also want to eat more.
"Sleep is a highly complex process designed to restore our bodies and minds through four phases that are repeated throughout the night forming the sleep cycle. These phases are vital for muscle repair, memory consolidation and release of hormones regulating growth and appetite," says Dr Sally Norton, NHS weight loss consultant and health expert at Vavista Life. "When we don't get enough sleep we struggle in all sorts of ways. We are less able to concentrate, make decisions or even control our own hunger! We are more likely to overeat more the next day (around 300 calories worth) in an attempt to get an energy fix. Studies even suggest that poor sleep may contribute to conditions like heart disease, diabetes and Alzheimer's - though more research is needed."
After a few nights
After several nights of poor sleep, you might find it harder to concentrate and make decisions, and you are more prone to accidents. You might feel down and blue: chronic sleep deprivation may lead to long-term mood disorders like anxiety and depression.
"When people have disturbed sleep, the effect this has on how we feel the following day can be extremely noticeable in both our physical and emotional health," says leading sleep expert Dr Neil Stanley. "Good sleep is as important to good health as diet and exercise and so it is important to try and get good sleep each and every night."
After a few weeks/months
"After a week of a lack of sleep you really have zero tolerance for anything, sex drive becomes non-existent, cognitive function is all over the place, you are lazy, lethargic, sugar cravings kick in, decision making is totally erratic and a feeling of instability ripples through you," says Jerry Sargeant, a life enhancement coach. "Your mind becomes shaky, fuzzy, clouded. It's hard to concentrate therefore functionality and performance in business or in sports can be as low as 5-15% of its optimum."
A prolonged lack of sleep can affect the immune system, meaning you're prone to picking up coughs and colds. It can also affect gut health, says nutritional therapist Claire Barnes: "It is important to realise that chronic disruption of our circadian rhythm can have detrimental effects on our health."
Not getting enough shut eye on a regular basis is associated with increases in heart rate and blood pressure, and could increase the risk of obesity. People sleeping fewer than seven hours a night tend to gain more weight and have a higher risk of becoming obese, studies suggest.
It is believed these people have reduced levels of leptin – the chemical that makes you feel full – and increased levels of the hunger-stimulating chemical ghrelin. The way the body processes glucose is also altered by a lack of sleep, meaning those who sleep less could also develop type 2 diabetes.
So there you have it. Sleep is incredibly important for both our physical and mental health. Find out how to improve your sleep here.
