What is the right amount of sleep each night and how could missing it RUIN your health?

Functioning on a measly four hours of sleep a night used to be a badge of honour for high-powered CEOs and world leaders.

Part of Margaret Thatcher’s fearsome reputation came from how little she slept. Donald Trump used to brag that some nights he would only get three hours.

But a wealth of scientific studies in recent years have unequivocally shown that not getting enough shut eye can lead to a host of life-threatening diseases.

Yet two-thirds of adults throughout all developed nations fail to get the recommended eight hours. 

There is a tiny subset of the population — about one in 4million of us — born with a gene that allows them to thrive on half of that amount.

But for the vast majority, routinely sleeping less than six or seven hours a night demolishes your immune system and significantly raises your risk of developing numerous forms of cancer.

A study of 60,000 middle-aged and elderly Britons, published this week, found those who regularly need to nap during the day were 12 per cent more likely to develop high blood pressure than their peers.

The researchers concluded the naps themselves were not the problem, and suggested they were a sign of poor quality sleep at night. 

Even moderate reductions in sleep for just a week can disrupt blood sugar so profoundly you would be classified as pre-diabetic.

Sleep deprivation also increases the risk of your coronary arteries becoming blocked and brittle, setting you on a path towards cardiovascular disease, stroke or heart failure. 

Maybe you’ve noticed you crave junk food when you’re tired? Too little sleep swells concentrations of a hormone that makes you feel hungry, while suppressing a hormone that tells you you’re satisfied. 

Routinely sleeping less than six or seven hours a night demolishes your immune system and significantly raises your risk of developing numerous forms of cancer. Even moderate reductions in sleep for just a week can disrupt blood sugar so profoundly you would be classified as pre-diabetic. Short sleeping also increases the risk of your coronary arteries becoming blocked and brittle, setting you on a path towards cardiovascular disease, stroke or heart failure. Perhaps you have noticed you crave junk food when you’re tired? Too little sleep swells concentrations of a hormone that makes you feel hungry, while suppressing a companion hormone that signals food satisfaction

Sleep also seems to be a key lifestyle factor that determines whether or not you will develop Alzheimer’s disease — with getting too much or not enough both linked to the disease.

Sleep disruption may also contribute to major psychiatric conditions, including depression and anxiety. It has even been linked to suicide.

So, how do you know whether you’re routinely getting enough sleep? A good rule of thumb is to ask yourself if you could fall back asleep at 10am or 11am. If the answer is yes, you are probably not getting the sufficient quantity and/or quality of sleep.

Cancer

Routinely not getting enough sleep has been linked to greater ‘wear and tear’ on our cells. This type of disruption to our genes is thought to give rise to cancerous tumours.

A 2019 study found people who work night shifts have 30 per cent more damage to their DNA compared to those who work normal hours.

HOW MUCH SLEEP SHOULD YOU GET? AND WHAT TO DO IF YOU STRUGGLE TO GET ENOUGH

Preschool (3-5 years): 10-13 hours

School-age (6-13 years): 9-11 hours

Teen (14-17 years): 8-10 hours

Young adult (18-25) 7-9 hours

Adult (26-64): 7-9 hours

Older adult (65 or more) 7-8 hours

Source: Sleep Foundation 

WHAT CAN I DO TO IMPROVE MY SLEEP? 

1) Limit screen time an hour before bed

Our bodies have an internal ‘clock’ in the brain, which regulates our circadian rhythm. 

Mobiles, laptops and TVs emit blue light, which sends signals to our brain to keep us awake.

2) Address your ‘racing mind’

Take 5-10 minutes before you go to sleep to sit with a notebook and write down a list of anything that you need to do the following day.

3) Avoid caffeine after 12pm

If you want a hot drink in the afternoon or evening, go for a decaffeinated tea or coffee.

4) Keep a cool bedroom temperature

Keep bedroom thermostats to around 18°C. During spring/summer try sleeping with your bedroom window open to reduce the temperature and increase ventilation.

5) Limit alcohol in the evenings

While you might initially fall into deep sleep more easily, you then wake up frequently during the night and have poorer deep sleep overall.

6) Supplement vitamin D

Vitamin D plays a role in sleep. Vitamin D is widely available online and from most pharmacies.

If you are unsure if this is appropriate or how much you need, seek advice from your GP.

7) Ensure sufficient intake of magnesium and zinc

Foods high in magnesium include spinach, kale, avocado, bananas, cashews, and seeds. 

Foods high in zinc include meat, oysters, crab, cheese, cooked lentils, and dark chocolate (70%+).

 

Researchers from the University of Hong Kong looked at around 50 doctors from two local hospitals, half of whom had to work during the night and only got two to four hours of sleep. The rest got seven or more.

In a 2010 study, researchers in Ohio linked sleeping less than six hours a night to a 50 per cent increased risk of bowel cancer.

With this type of cancer being the second deadliest in the UK and US, the Case Western Reserve University study concluded that short sleep is a ‘public health hazard’.

In addition to DNA damage, insufficient sleep may affect cancer by suppressing levels of key hormones in the body.

Melatonin is key to making us feel sleepy. Throughout the day, levels of the hormone remain very low in the body but as the day wears on, its production increases and the end result is that you feel tired.

But melatonin levels can be suppressed by not enough or fragmented sleep.

A lack of sleep may also indirectly heighten cancer risk – by making us hungrier and fatter.

In 2012, research published in the journal PLoS One looked at the cancer risk in nearly 25,000 middle-aged adults across Europe.

It found people who slept less than six hours per night were 43 per cent more likely to develop cancer in their lifetime than those who got seven or more hours.

A separate 2019 study found patients who slept six or less hours a night were nearly three times more likely to die from cancer within 30 years than those who got seven hours or more.

Researchers from Penn State University looked at 1,654 adults aged 20 to 74 who had a history of heart disease or stroke.

Those who were sleep deprived had a 2.92-times greater risk of dying from any cancer within three decades than those who got sufficient rest, according to the paper published in the Journal of the American Heart Association.

Heart problems

The link between an unhealthy sleeping pattern and an  unhealthy heart is becoming undeniable.

As we approach midlife, and our body and health begin to deteriorate, the impact of insufficient sleep on the cardiovascular system escalates.

Adults aged 45 or older who sleep fewer than six hours a night are 200 per cent more likely to have a heart attack or stroke during their lifetime, compared with those sleeping seven to eight hours a night.

This finding, from a 2012 study by Chicago University, emphasises how important it is to prioritise sleep in midlife — which is unfortunately the time when family and professional circumstances encourage us to do the exact opposite.

It doesn’t take much sleep deprivation to impact your cardiovascular system. One night of modest sleep reduction — even just one or two hours — will promptly speed the contracting rate of a person’s heart, hour upon hour.

This also causes a significant increase in systolic blood pressure, which puts greater strain on the heart and blood vessels.

You will find no solace in the fact that the experiments that confirmed this were conducted in young, fit individuals, all of whom started out with an otherwise healthy cardiovascular system just hours before. 

Beyond accelerating your heart rate and increasing your blood pressure, a lack of sleep damages those strained blood vessels.

The coronary arteries, which supply the heart with blood, are especially affected. These need to be clean and stay open wide at all times.

If these passageways are narrowed or blocked, your heart can suffer a comprehensive — and often fatal — attack caused by blood oxygen starvation.

Donald Trump famously got as little as three hours of sleep per night - but rumour has it he made up for his lack of sleep by napping during the day

Donald Trump famously got as little as three hours of sleep per night – but rumour has it he made up for his lack of sleep by napping during the day

One cause of a coronary artery blockage is atherosclerosis, where hardened plaques which contain calcium deposits build up in the arteries.

There is also a yearly ‘global experiment’ that involves 1.5 billion people and highlights the link between a poor night of sleep and our heart health.

In the Northern Hemisphere, the switch to daylight saving time in March results in most people losing an hour of sleep. 

Researchers have tabulated millions of hospital records and discovered that this seemingly trivial sleep reduction comes with a frightening spike in heart attacks the following day.

It works both ways. In the autumn, rates of heart attacks plummet the day after the clocks go back, when we gain an hour of sleep.

A similar rise-and-fall relationship can be seen with the suicide rate, as well as the number of traffic accidents.

This proves that the brain, by way of attention lapses, microsleeps and emotional instability, is just as sensitive as the heart to very small disruptions in sleep.

WHY DO WE NEED SLEEP? 

Sleep dispenses a multitude of health-ensuring benefits — and they’re yours to pick up as a repeat prescription every 24 hours, should you choose.

It enriches a diversity of functions within the brain, including our ability to learn, memorise and make logical decisions.

Sleep also recalibrates our emotional brain circuits, allowing us to navigate the social and psychological challenges of the next day with cool-headed composure.

We are even beginning to understand the most impervious of all conscious experiences: the dream.

Dreaming provides a unique set of benefits, including soothing painful memories and inspiring creativity, as I will be explaining next week.

Downstairs in the body, sleep restocks the armoury of our immune system, helping to fight malignancy, preventing infection and warding off all manner of illnesses.

Sleep also reforms the body’s metabolic state by fine-tuning the balance of insulin and circulating glucose. It regulates our appetite, helping to control body weight by encouraging healthy food selection rather than impulsive choices.

It is also needed to maintain a flourishing microbiome within your gut, where so much of our nutritional health begins.

Adequate sleep is also closely tied to the fitness of our cardiovascular system, lowering blood pressure while keeping our hearts in fine condition. 

Recall the last time you had the flu. Miserable, wasn’t it? Runny nose, aching bones, sore throat, heavy cough and a total lack of energy. You probably just wanted to curl up in bed and sleep. As well you should.

Your body is trying to sleep itself well. Sleep fights against infection and sickness by deploying weaponry from your immune arsenal and cladding you with protection.

When you do fall ill, the immune system actively stimulates the sleep system, demanding more bed rest to help reinforce the war effort. Reduce sleep for even a single night, and that invisible suit of immune armour is rudely stripped from your body.

Dementia 

A growing body of evidence shows not getting enough sleep in middle-age is linked to dementia later in life.

It’s thought that when we don’t sleep long enough, we don’t give the brain the time to drain away beta amyloid and other plaques. 

This allows the substances to continue to accumulate, day after day, until they cause the memory-robbing disorder.

A study of 8,000 Britons aged 50 to 70 last year found those who got fewer than six hours sleep a night in middle-age had a 30 per cent higher risk of late-onset dementia.

And separate research by Cambridge University in 2021 found people who got more or less than seven hours per night scored worse in tests for thinking speed, attention span, memory and problem-solving – all early hallmarks of dementia.

The researchers examined data from 498,277 adults aged 38 to 73, gathered from the UK Biobank — a database of patients monitored for 10 years.

Similar results were produced by researchers at Stanford University, who followed Americans aged 65 to 85 in a study published last August. 

Because dementia itself usually disrupts people’s sleep, there is still a questions about whether the lack of sleep caused the disease in the first place or is simply a symptom of it.

Obesity

Short sleep duration may lead to obesity through an increase of appetite via hormonal changes caused by sleep deprivation. 

Lack of sleep produces ghrelin, a hormone which, among other effects, stimulates appetite.

Sleep deprivation is also associated with growth hormone deficiency and elevated cortisol levels, both of which have been linked to obesity.

Insufficient sleep can also slow down your metabolism.

A 2006 study of 75,000 children and adults by the University of Warwick’s Medical School found those who sleep less have a greater increase in body mass and waist circumference over time.

At all ages short sleepers gained more weight and overall were up to twice as likely to become overweight or obese. Short sleepers were defined as having less sleep than the reference category for their age.

Meanwhile, a study published earlier this month found sleeping with a light on at night were 80 per cent more likely to be obese than those who slept in darkness.

The research, by Northwestern University experts, looked at 552 people between the ages of 63 and 84. Having lamps on at night can disrupt the body’s natural circadian rhythm and melatonin production, which decreases the quality of our sleep.

Darkness prompts the pineal gland to start producing melatonin while light causes that production to stop. Sleep also reforms the body’s metabolic state by fine-tuning the balance of insulin and circulating glucose. 

It is also needed to maintain a flourishing microbiome within your gut, where so much of our nutritional health begins.

Weakened immunity  

It’s happened to us all. You don’t get enough sleep for a few nights in a row and all of a sudden you come down with a nasty cold.

It’s not a coincidence. 

Sleep restocks the armoury of our immune system, helping to fight malignancy, preventing infection and warding off all manner of illnesses. 

When you do fall ill, the immune system actively stimulates the sleep system, demanding more bed rest to help reinforce the war effort. 

Reduce sleep for even a single night, and that invisible suit of immune armour is rudely stripped from your body. 

Sleep deprivation has been shown to suppress the production of antibodies and T-cells, which are vital for fighting infections.

In 2019, scientists at the University of Tuebingen in Germany compared T cells from volunteers who were allowed to sleep for eight hours and those who stayed awake all night.

They found levels in the sleep deprived group had a much lower ability to bind to a key molecule featured in the immune response. 

A separate study found levels of a key immune cell called a ‘natural killer’ cell were reduced by more than 70 per cent in people who don’t get enough sleep.

Research has even shown that under-slept people are less likely to get a full immune response from vaccines.

In 2002, scientists showed adults who were immunised against flu developed antibody concentrations half the level of their well-rested peers.

Researchers have also found that people who slept fewer than six hours per night are, on average, far less likely to mount an antibody response to the hepatitis B jab.

They were nearly 12 times more likely to be unprotected by the vaccine than people who slept more than seven hours, according to the 2012 study.

Low sex drive

For the long-suffering wives of workaholic men it may well come as no surprise.

Not getting enough sleep at night may kill men’s sex drives.

A study by the University of Chicago in 2011 found those who sleep for less than five hours a night for periods of longer than a week have significantly lower levels of testosterone than those who get a full night’s rest.

And with testosterone affecting men’s libido and energy levels, those who miss out on sleep are much more likely to be put off sex.

The affect is so drastic it reduces the hormone to levels more akin to someone 15 years older, they reported in the Journal of the American Medical Association.

Another study in the Journal of Clinical Sleep Medicine found a third of men with sleep apnoea also experience lower testosterone levels.

In young, healthy men, testosterone levels were decreased by 10 to 15 per cent after a week of sleep restriction to five hours per night.

The researchers found that the effects of restricting sleep on testosterone levels were especially evident between 2pm and 10pm the next day.

Low testosterone levels are associated with reduced well-being, vigour and erections.

Diabetes

Research shows that poor or not enough deep sleep has a dramatic effect on the body’s metabolism and the conversion of sugar into energy, heightening the risk of diabetes.

Just three nights of disrupted sleep can have the same effect on the body’s ability to control sugar levels as putting on more than two stone in weight and being in a pre-diabetic state.

In April this year, Bristol University researchers collected data on more than 330,000 adults from the UK Biobank, most of whom were in their 50s.

People who said they regularly struggled to sleep had higher blood sugar levels — a marker of type 2 diabetes.

The team calculated that treating insomnia could trigger a drop in blood sugar levels comparable to losing 14kg (2st 3lbs).

They didn’t suggest a biological mechanism for their findings, published in Diabetes Care.

But earlier studies have found sleep deprivation increases insulin resistance, levels of stress hormone cortisol and inflammation in the body, all of which can have an effect on blood sugar.

A 2007 study by the University of Chicago study in 2007 looked at the effect of sleep quality on the body’s ability to produce insulin, the hormone needed to control blood glucose or sugar levels.

Nine healthy young men and women were monitored during five nights of sleep.

During the first two nights, they were allowed to sleep normally. After that, their sleep was regularly disrupted by noises calculated to be loud enough to draw them out of deep sleep without fully waking them.

The disruption to deep sleep was equivalent to that seen during the ageing process, with the young volunteers experiencing a quality of sleep more usually seen in people in their 60s.

After normal sleep and interrupted sleep the volunteers were given injections of glucose and their blood was sampled to measure how well the sudden influx of sugar was being controlled.

Analysis showed that sleep quality had a big effect on the body’s ability to use insulin to control blood sugar levels, with levels rising by an alarming 23 per cent after just three nights of interrupted sleep.

Such an inability to use insulin – or insulin resistance – is thought to be the main cause of type-2 diabetes, which is linked to obesity and affects more than one million Britons.

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