Why good night’s sleep is best medicine, by studies
Sleep can boost the immune system by making white blood cells more able to attack, a study has found.
When we are awake, there are more stress hormones such as adrenaline in the body, which researchers have discovered slow down parts of the immune system.
The reduced function is associated with conditions including cancerous tumour growth, malaria infection and stress, experts said.
Research also suggests why people with difficulty sleeping may end up with a weakened immune system and be more at risk of chronic stress and depression.
Researchers have shown sleep improves the potential ability of some of the body’s immune cells to attach to their targets.
Their findings, published in the Journal of Experimental Medicine, help explain how sleep can fight off an infection.
The research focused on T cells – a type of white blood cell, which is critical to the body’s immune response and recognises and kills dangerous invading cells.
When T cells recognise a specific target, such as a cell infected with a virus, they activate sticky proteins known as integrins, which attach to their target and, in the case of a virally infected cell, kill it.
While much is known about the signals which activate integrins, less well understood are the signals that may affect T cells’ ability to attach to their targets.
Researchers at the University of Tübingen in Germany, led by Dr Stoyan Dimitrov, compared T cells taken from 10 healthy volunteers while they slept or stayed awake all night.
All participants took part in two experiments – in one they would sleep from 11pm to 7am and in the other they would stay awake during that time, talking or listening to music.
T cells taken on the night of sleep showed ‘significantly higher’ levels of integrin activation than T cells taken when they were awake.
This is believed to be because, while the participants were asleep, they had lower numbers of certain signalling molecules which hamper immune activity while awake.
These molecules are thought to be boosted by the hormones adrenaline and noradrenaline – which are known to be higher in people who are stressed.
Adrenaline levels dip while the body is asleep.
Dimitrov said: “The levels of these molecules needed to inhibit integrin activation are observed in many pathological conditions, such as tumour growth, malaria infection, hypoxia and stress.
“This pathway may therefore contribute to the immune suppression associated with these pathologies.”
Study co-author Dr. Luciana Besedovsky said: “Our findings show that sleep has the potential to enhance the efficiency of T cell responses, which is especially relevant in light of the high prevalence of sleep disorders and conditions characterised by impaired sleep, such as depression, chronic stress, ageing, and shift work.”
In addition to helping explain the beneficial effects of sleep and the negative effects of conditions such as stress, the research team said the study could spur the development of new ways to improve the ability of T cells to attach to their targets.
“Dimitrov added: ‘This could be useful, for example, for cancer immunotherapy, where T cells are prompted to attack and kill tumour cells.”
Meanwhile, a lack of sleep could permanently damage Deoxy ribonucleic Acid (DNA)/genetic material and increase the risk of cancer, scientists believe.
Sleep deprivation can also reduce DNA’s ability to repair itself, possibly leading to genetic diseases, findings from a study suggest.
Researchers believe it is the first study of its kind to look into the effects of sleep deprivation on genes in young adults.
The research focused on doctors who had to adjust their sleep patterns due to night shift work. Scientists do not know why a lack of sleep damages DNA.
The recommended amount of sleep is generally seven hours a night, but figures suggest adults routinely miss out on an hour or two.
The study at The University of Hong Kong looked at 49 working doctors from two local hospitals, 24 of whom had to work overnight on-site calls.
When a doctor receives such a call – on average they get five to six per month – they must work from late afternoon to early morning the next day.
In the study the participants got between two and four hours of sleep during calls, with three getting as little as a single hour’s shut-eye.
The remaining 25 doctors were not expected to work these hours. Researchers took blood samples from all doctors after they had had three nights of healthy sleep.
Then blood samples were taken the morning after a night shift when doctors were sleep deprived.
The findings, published in the journal Anaesthesia, showed doctors who worked night shifts had 30 per cent more breaks in their DNA compared to those who did not.
What’s more, the DNA damage increased a further 25 per cent after a night of sleep deprivation.
DNA repair was also lower in the doctors who didn’t get adequate sleep, which can cause cell death.
The study authors wrote: “DNA damage is a change in the basic structure of DNA that is not repaired when the DNA is replicated.
“Double‐strand breaks are particularly hazardous, as repair failure causes genomic instability and cell death, whereas disrepair can lead to inappropriate end‐joining events that commonly underlie oncogenic transformation [cancer formation].
“Sleep deprivation in shift workers is associated with adverse health consequences.
“Increased DNA damage has been linked to the development of chronic disease. This study demonstrates that disrupted sleep is associated with DNA damage.”
Although the findings are preliminary, Dr Gordon Wong Tin-chun, co-author of the study and an associate professor at HKU’s department of anaesthesiology, said there is an indication the sleep disruption is ‘not good’ for your genes.
He said: “[Such conditions] may increase chances of developing diseases from genetic mutations such as cancers.”
It is not clear, according to the researchers, why DNA damage occurs due to a lack of sleep.
Wong Tin-chun said the findings of the study might be applicable to people who had shift patterns similar to doctors.
They hope the study will raise awareness on the importance of getting enough sleep.
The study also highlighted the doctors it focused on were ‘young and healthy’, and therefore more tolerant of a lack of sleep.
“Maybe you should consider looking into your [sleep habits] and treating sleep with a bit more respect,” Wong Tin-chun said.
The recommended hours of sleep for people vary across age groups.
An adult aged between 18 and 60 should get at least seven hours of sleep per night, according to the website of the US Centers for Disease Control and Prevention.
Regular poor sleep puts you at risk of serious medical conditions, including obesity, heart disease and diabetes.