Sleeping in over the weekend is one of life’s great pleasures. Yet some of us are much better at it than others. A teenager is much more likely to emerge from their bed at midday than their middle-aged parents – but even within age groups, individual differences exist.
Why is this? It’s well-known that teenagers tend to sleep later than mature adults, and we all have our natural rhythms. But we’re not actually the slaves to our body clocks you might think. If you find getting out of bed on a Sunday hard even after a long night’s sleep, there may be something you can do about it.
The body clock generates rhythms so that we are alert during the day while body temperature is high and sleep at night while body temperature is low. This clock has evolved to match the cycle of light and dark, and associated cycles of temperature, for example, created by the Earth’s rotation. But what happens now that artificial light means that we are in control of this cycle?
Seeing the light
Back in the 1960s, Jurgen Aschoff and Rutger Wever studied sleep and body temperature rhythms in humans. They placed volunteers in windowless basements and underground bunkers with no access to the natural 24-hour light and dark cycle and no timepieces.
Health news in pictures
Health news in pictures
1/22 New online test predicts skin cancer risk
Health experts have created a new online tool which can predict a person’s risk of developing a common form of skin cancer. The tool uses the results of a 10-question-quiz to estimate the chance of a person aged 40 or over of having non-melanoma skin cancers within three years. Factors including the age, gender, smoking status, skin colour, tanning ability, freckling tendency, and other aspects of medical history are covered by the quiz
2/22 Multiple Sclerosis stem cell treatment 'helps patients walk again'
A new treatment for multiple sclerosis (MS) has enabled some patients to walk again by “rebooting” their immune systems. As part of a clinical trial at Sheffield's Royal Hallamshire Hospital involving around 20 patients, scientists used stem cells to carry out a bone marrow transplant. The method known as an autologous haematopoietic stem cell transplant (HSCT) works by using chemotherapy to destroy the area of the immune system which causes MS
3/22 Dementia patients left without painkillers and handcuffed to bed
Dementia patients experience a ‘shocking’ variation in the quality of hospital care they receive across England, a charity has warned. Staff using excessive force and not giving dementia patients the correct pain medication were among the findings outlined in a new report by The Alzheimer’s Society, to coincide with the launch of Fix Dementia Care campaign
4/22 Cancer risk 'increased' by drinking more than one glass of wine or pint of beer per day
Drinking more than one glass of wine or pint of beer a day increases the risk of developing cancer, according to medical experts. New guidelines for alcohol consumption by the UK published by chief medical officers warn that drinking any level of alcohol has been linked to a range of different cancers. The evidence from the Committee on Carcinogenicity (COC) overturns the oft-held view that a glass of red wine can have significant medical benefits for both men and women
5/22 Vaping 'no better' than smoking regular cigarettes
Vaping could be “no better” than smoking regular cigarettes and may be linked to cancer, scientists have found. The study which showed that vapour from e-cigarettes can damage or kill human cells was publsihed as the devices are to be rolled out by UK public health officials as an aid to quit smoking from 2016. An estimated 2.6 million people in the UK currently use e-cigarettes
6/22 Rat-bite fever
A teenager was hospitalised and left unable to move after she developed the rare rat-bite fever disease from her pet rodents which lived in her bedroom. The teenager, who has not been named, was taken to hospital after she complained of a pain in her right hip and lower back which later made her immobile, according to the online medical journal BMJ Case Reports. She suffered for two weeks with an intermittent fever, nausea and vomiting and had a pink rash on her hands and feet. The teenager, who had numerous pets including a dog, cat, horse and three pet rats, has since made a full recovery after undergoing a course of antibiotics. Blood tests showed that she was infected with for streptobacillus moniliformis – the most common cause of rat-bite fever. One of her three pet rats lay dead in her room for three weeks before her symptoms showed
7/22 Taking antidepressants in pregnancy ‘could double the risk of autism in toddlers’
Taking antidepressants during pregnancy could almost double the risk of a child being diagnosed with autism in the first years of life, a major study of nearly 150,000 pregnancies has suggested. Researchers have found a link between women in the later stages of pregnancy who were prescribed one of the most common types of antidepressant drugs, and autism diagnosed in children under seven years of age
8/22 Warning over Calpol
Parents have been warned that giving children paracetamol-based medicines such as Calpol and Disprol too often could lead to serious health issues later in life. Leading paediatrician and professor of general paediatrics at University College London, Alastair Sutcliffe, said parents were overusing paracetamol to treat mild fevers. As a result, the risk of developing asthma, as well as kidney, heart and liver damage is heightened
9/22 Fat loss from pancreas 'can reverse' effects of type-2 diabetes
Less than half a teaspoon of fat is all that it takes to turn someone into a type-2 diabetic according to a study that could overturn conventional wisdom on a disease affecting nearly 3 million people in Britain. Researchers have found it is not so much the overall body fat that is important in determining the onset of type-2 diabetes but the small amount of fat deposited in the pancreas, the endocrine organ responsible for insulin production
10/22 Potatoes reduce risk of stomach cancer
Scientists have found people who eat large amounts of white vegetables were a third less likely to contract stomach cancer. The study, undertaken by Chinese scientists at Zhejiang University, found eating cauliflower, potatoes and onions reduces the chance of contracting stomach cancer but that beer, spirits, salt and preserved foods increased a person’s risk of the cancer
11/22 Connections between brain cells destroyed in early stages of Alzheimer’s disease
Scientists have pinpointed how connections in the brain are destroyed in the early stages of Alzheimer’s disease, in a study which it is hoped will help in the development of treatments for the debilitating condition. At the early stages of the development of Alzheimer’s disease the synapses – which connect the neurons in the brain – are destroyed, according to researchers at the University of New South Wales, Australia. The synapses are vital for brain function, particularly learning and forming memories
12/22 Sugar tax
The Government should introduce a sugar tax to prevent an “obesity crisis” from crippling the NHS, a senior Conservative MP and former health minister has said. Dr Dan Poulter believes that the case for increased taxes on unhealthy sugary products was “increasingly compelling”
13/22 Cancer breakthrough offers new hope for survivors rendered infertile by chemotherapy
A potentially “phenomenal” scientific breakthrough has offered fresh hope to cancer patients rendered infertile by chemotherapy. For the first time, researchers managed to restore ovaries in mice affected by chemotherapy so that they were able to have offspring. The scientists now plan to begin clinical trials to see if the technique, which involves the use of stem cells, will also work in humans by using umbilical cord material and possibly stem cells taken from human embryos, if regulators agree
14/22 Take this NHS test to find out if you have a cancerous mole
An interactive test could help flag up whether you should seek advice from a health professional for one of the most common types of cancer. The test is available on the NHS Choices website and reveals whether you are at risk from the disease and recommends if you should seek help. The mole self-assessment factors in elements such as complexion, the number of times you have been severely sunburnt and whether skin cancer runs in your family. It also quizzes you on the number of moles you have and whether there have been any changes in appearance regarding size, shape and colour
15/22 Health apps approved by NHS 'may put users at risk of identity theft'
Experts have warned that some apps do not adequately protect personal information
16/22 A watchdog has said that care visits must last longer
The National Institute for Health and Care Excellence (Nice) said home help visits of less than 30 minutes were not acceptable unless part of a wider package of support
17/22 Pendle in Lancashire tops list of five most anxious places to live in the UK
Pendle in Lancashire has been named the most anxious place to live in the UK, while people living in Fermanagh and Omagh in Northern Ireland have been found to be the happiest
18/22 Ketamine could be used as anti-depressant
Researchers at the University of Auckland said monitoring the effects of the drug on the brain has revealed neural pathways that could aid the development of fast-acting medications. Ketamine is a synthetic compound used as an off anaesthetic and analgesic drug, but is commonly used illegally as a hallucinogenic party drug. Dr Suresh Muthukumaraswamy, a senior researcher at the university and a member of the institution’s Centre for Brain Research, used the latest technology in brain imaging to investigate what mechanisms ketamine uses to be active in the human brain
19/22 A prosthetic hand that lets people actually feel through
The technology lets paralysed people feel actual sensations when touching objects — including light taps on the mechanical finger — and could be a huge breakthrough for prosthetics, according to its makers. The tool was used to let a 28-year-old man who has been paralysed for more than a decade. While prosthetics have previously been able to be controlled directly from the brain, it is the first time that signals have been successfully sent the other way
20/22 The biggest cause of early death in the world is what you eat
Unhealthy eating has been named as the most common cause of premature death around the globe, new data has revealed. A poor diet – which involves eating too few vegetables, fruits, nuts and grains and too much red meat, salt and sugar - was shown to be a bigger killer than smoking and alcohol
21/22 Scientists develop blood test that estimates how quickly people age
Scientists believe it could be used to predict a person’s risk of developing Alzheimer’s disease as well as the “youthfulness” of donated organs for transplant operations. The test measures the vitality of certain genes which the researchers believe is an accurate indication of a person’s “biological age”, which may be younger or older than their actual chronological age
22/22 Aspirin could help boost therapies that fight cancer
The latest therapies that fight cancer could work better when combined with aspirin, research has suggested. Scientists from the Francis Crick Institute in London say the anti-inflammatory pain killer suppresses a cancer molecule that allows tumours to evade the body’s immune defences. Laboratory tests have shown that skin, breast and bowel cancer cells often generate large amounts of this molecule, called prostaglandin E2 (PGE2). But Aspirin is one of a family of drugs that sends messages to the brain to block production of PGE2 and this means cancer cells can be attacked by the body’s natural defences
In most experiments, the lights were turned on continuously and volunteers had no control over the light-dark cycle (except by closing their eyes during sleep). But in some experiments, the volunteers could turn off the lights when they wanted to go to sleep and on again when they woke up. Those volunteers in control of the light-dark cycle found their sleep patterns and the rhythm of their core body temperature shifted to later in the day. And in more than 40% of these cases, sleep was no longer synchronised with their body temperature.
Hunter-gatherers who only have campfires as sources of artificial light go to sleep several hours after sunset and wake up around dawn. But while the light of a small fire won’t influence our body clock, the artificial light we are exposed to in the evening can. Specifically, it prevents the synthesis of the sleep-facilitating hormone melatonin and suppresses sleepiness.
When you stay up well past sunset and then have to go to work the next morning, you wake up because of the alarm clock not because your body is ready. But it’s not the alarm clock’s fault that you’re not getting enough sleep. In a way we place ourselves in an Aschoff-Wever bunker every evening. Why turn off the lights and go to bed when you are not sleepy? You’d rather continue to work, socialise or relax.
As a result, your body clock is driven out of synch with the natural light-dark cycle. At the weekend, you may go to sleep at the same time or even later, and then sleep until you have paid-off your sleep debt and your body clock finally tells you that it is time to wake up.
This difference in sleep timing between the working week and the weekend has been referred to as social jet lag. It is often implied that it is our early work schedules or early school times or our body clocks that are causing the problems, but that doesn’t follow from the example above. Our ability to disrupt our body clocks with powerful artificial light is at least partly to blame.
The difference between sleep duration during the week and the weekend is greatest in adolescents and young adults and then declines steadily as we get older. This is partly because our need for sleep actually declines with age. Teenagers may need nine hours or more but this falls to seven or eight by the time you reach your fifties. So even when a teenager and middle-aged person have similar work and sleep schedules during the week, the accumulated sleep debt and difference between week and weekend sleep will be greater in the adolescent.
Yet within a group of adults of similar ages, some will sleep later and longer during the weekend than others. Without the confounding effects of artificial light, some of us have naturally fast body clocks that effectively run for less than 24 hours, and many of us have slow clocks that run for more than 24 hours. Those with a slow clock, delay sleep more during the week and then sleep longer during the weekend.
There are also other individual differences that can contribute to the variation in weekend sleep habits. Some of us are more sensitive to evening light than others, meaning our melatonin is more suppressed. This can lead to later bedtimes, a greater sleep debt, a later clock and ultimately later and longer sleeps over the weekend.
By taking a biological perspective on the regulation of sleep timing and recognising how we have divorced ourselves from the natural world and influence our biology in unwanted ways by behavioural choices, we may understand individual differences in weekend sleep habits. So don’t just blame your alarm clock. By making more time for sleep during the week, reducing excessive light exposure in the evening and by making sure you see some light in the morning, you may reduce your social jet lag and wake up feeling more refreshed.