Tuesday February 26 2013
It is thought that a third of people in the UK have bouts of insomnia
“Lack of sleep for just a few nights can kill”, reports the Daily Express. However, tired and anxious Express readers can safely ignore this headline.
The story – which Sky News more accurately reports as “Lack of sleep impacts on gene activity” – is based on the results of a tiny trial in which healthy people had samples of their blood analysed following a period of total sleep deprivation after either:
- a week of less than six hour’s sleep a night
- a week of up to 10 hour’s sleep a night
The blood samples were used to measure RNA levels – RNA acts like a ‘messenger’ by carrying information needed to make proteins from genes to the protein-making machinery.
The researchers found there were significant differences in RNA levels in the insufficient sleep group when compared to the sufficient sleep group. These differences corresponded to genes known to be involved in a wide variety of processes, including immunity and stress.
Most of the media’s reporting of the study has over-interpreted these results to suggest that poor sleep leads to changes in RNA, which in turn, leads to poor health. However, this study did not look at the effects of these RNA changes on health, especially in the long-term. It was also a tiny and rather artificial trial that is unlikely to be applicable to the wider population.
While it is sensible to aim to get a good night’s sleep, the findings of this study should not keep you awake at night.
Where did the story come from?
The study was carried out by researchers from the University of Surrey and was funded by an Air Force Office of Scientific Research Grant and by a Biotechnology and Biological Sciences Research Council Grant.
The study was published in the peer-reviewed Proceedings of the National Academy of Sciences (PNAS) journal. The study is freely available online through the PNAS open access option.
The results of this study were widely reported by the media, and the accuracy of the coverage varied considerably.
There was very good reporting, for example “sleeping less than six hours a night skews activity of hundreds of genes” in The Guardian. However, this contrasts with the Express, which offered up the scaremongering and inaccurate headline ‘Lack of sleep for just a few nights can kill’. This completely inappropriate headline is made somewhat worse by the fact that the actual reporting in the main body of the Express story is really very good.
What kind of research was this?
This was a crossover trial. In crossover trials, people participate in one arm of the trial, and then ‘crossover’ to the other arm of the trial. This means the participants in both arms of the trial are the same.
This was a small trial of only 26 participants (14 men, 12 women), with an average age of 27.5 years, who slept 8.2 hours a night on average.
It is not clear how applicable the findings of this research are to the wider population, for example people of different ages, shift workers, or those people who normally sleep six hours a night.
From this study, the long-term effects of insufficient sleep cannot be determined, although the researchers report that short sleep duration has been found to be associated with negative health outcomes in other studies.
It also remains to be seen whether the changes in the levels of RNA seen in this study are associated with these negative health outcomes.
What did the research involve?
Participants in this study stayed in the clinical research centre at the University of Surrey during the trial. After two normal nights to allow participants to become familiar and comfortable with their surroundings, participants were allowed to have:
- a period of six hours to sleep per night for seven consecutive nights (‘the insufficient sleep protocol’)
- ten hours to sleep per night for seven consecutive nights (‘the sufficient sleep protocol’ – which acted as a control condition)
After the seven nights, participants in both conditions were subjected to a period of ‘extended wakefulness’ (39 to 41 hours of sleep deprivation). During this period, blood samples were taken to monitor melatonin levels and the levels of RNA.
The participants were then given a 12-hour sleep recovery opportunity before being discharged.
After at least 10 days, participants returned to the clinical research centre to participate in the other arm of the study.
The researchers then analysed how sleep restriction affected the levels of different RNAs in the blood, and the time they were produced.
What were the basic results?
The researchers found that after seven days of insufficient sleep, the levels of RNA in the blood from 711 genes were either higher or lower than after sufficient sleep.
The researchers then looked at levels of RNAs that had a ‘circadian rhythm’, meaning that they fluctuated over a period of 24 hours in response to the body’s internal clock. They found that after insufficient sleep, the number of genes producing RNAs in the blood with a circadian rhythm decreased from 1,855 to 1,481. The amount of variation was also decreased.
During the period of extended wakefulness at the end of the study arms:
- RNA from 122 genes responded if participants had sufficient sleep
- RNA from 856 genes responded if participants had insufficient sleep
The RNAs affected by insufficient sleep included genes associated with metabolism, inflammation, the immune system, stress responses and sleep homeostasis (a regulatory system that ‘tells’ the body when to sleep and when to wake up).
How did the researchers interpret the results?
The researchers concluded that, “this study has demonstrated that insufficient sleep to an extent frequently or chronically experienced by many individuals in industrialised societies altered the temporal organisation of the human blood transcriptome [levels of RNA], including its circadian regulation and response to acute sleep loss”.
They go on to say that the RNAs whose levels were different after insufficient sleep, “might be involved in the negative effects of sleep loss on heath, and highlight the interrelatedness of sleep homeostasis, circadian rhythmicity and metabolism.”
This small crossover study found that insufficient sleep causes changes in the levels of RNA in the blood. However, there are some important limitations:
- Only a week of insufficient sleep compared to a week of sufficient sleep was examined. It is not known whether the RNA changes indicate what would happen in the longer term if a person continuously had less than six hours of sleep a night, for example over a number of years.
- The people in this trial were all young, healthy adults who normally got around eight hours sleep a night, so it is not clear if the findings of this research would apply to the wider population. It is entirely possible that people who were ‘used to’ sleeping for fewer hours each night would not display the same changes.
- The small sample size means that the results may not even be applicable to the population group being studied – another sample of 26 young, healthy adults who normally had eight hours sleep a night could show different results.
- The experimental scenario of giving participants the hours for insufficient or sufficient sleep at a clinical research centre may not be directly comparable to the real-life situation of sleeping at home, where there may be the attendant distractions or stresses of everyday life.
- Crucially, the long-term health impacts of the changes in RNA seen are unknown.
While it seems sensible advice to aim to get a good night’s sleep, missing a few hours certainly isn’t going to kill you – as the Express claimed.
If you do experience persistent bouts of insomnia that are having an adverse effect on your quality of life and daily functioning then you should contact your GP for advice.
Read more about the treatment of insomnia.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.