Tuesday September 3 2013
Three in 10 Britons suffer from insomnia
Insomniacs find it harder than good sleepers to concentrate during the daytime, was how BBC News reported on a study on brain activity among people with and without poor sleep.
Meanwhile, the Mail Online and The Daily Telegraph ran with the opposite and less accurate angle that people with poor concentration (‘daydreamers’) suffered insomnia.
The stories are based on a US study comparing findings from brain scans of 25 people with insomnia and 25 people who were considered good sleepers, carried out while they performed memory tests. The researchers say they found variations in brain activity between poor sleepers and good sleepers.
Three in 10 Britons suffer from insomnia, which is defined as difficulty getting to sleep, difficulty staying asleep or having non-refreshing sleep. Persistent insomnia can affect personal lives and performance at work, it is also a major cause of depression.
This was a small study that only included people who were relatively young (the average age was 32 years). Also, most of the participants with insomnia were considered to have moderate severity insomnia. Larger studies with people of different ages and severities of disease are needed to draw firmer conclusions about differences in brain activity while performing memory tasks.
Where did the story come from?
The study was carried out by researchers from the University of California and San Diego State University. It was funded by a grant from Actelion Pharmaceuticals Ltd and two of the researchers reported receiving consulting fees from Actelion Pharmacueticals Ltd. No other interests were reported. The study was published in the peer-reviewed journal: Sleep.
The media’s reporting of the story was varied; the BBC news accurately reported the study findings, while the Mail did not. The study did not look at whether people who were ‘daydreamers’ developed insomnia, so this headline is misleading. Once past the headline, the Mail also incorrectly reports that the findings ‘mean sufferers [of insomnia] usually put more effort into daytime jobs than healthy sleepers’. As the study did not look at the effect of insomnia on daytime jobs, these conclusions cannot be drawn.
What kind of research was this?
This was an experimental study that compared people with insomnia to people who were considered good sleepers and looked at differences in performance and brain activity on functional MRI during a memory task with different levels of difficulty. The researchers say the study allowed evaluation of whether people with insomnia responded differently to increasingly challenging memory tests.
What did the research involve?
Researchers recruited 25 people with insomnia (referred to as ‘primary insomnia’) and 25 people without insomnia (referred to as ‘good sleepers’), who acted as controls. To be eligible all the participants had to meet the following criteria:
- have a stable sleep schedule with a preferred sleep phase between 10pm and 8am
- be aged 25 to 50 years
- not be taking any over-the-counter sleep medications or medications for psychosis
- not have depression (participants with a single past episode of depression were able to be included)
Insomnia was assessed using the Duke Structured Interview for Sleep Disorders and to be included, participants had insomnia confirmed using this assessment as well as a 7 to 10 day sleep diary. These participants all had sleep difficulties for three or more nights per week lasting three or more months. They also had an average of 45 minutes or more of wake time after lights went out and either less than six hours of total sleep time or had a ‘sleep efficiency’ of less than 80% (sleep efficiency was not further defined).
‘Good sleepers’ also underwent an interview and completed a sleep diary, and to be included they had to meet the following criteria:
- report a total of 7 to 9 hours total sleep time per night
- have an average ‘sleep efficiency’ of 90% or more
- take less than one daytime nap per week
- have no daytime performance complaints (not further defined)
Each person with primary insomnia was matched to a good sleeper, taking into consideration the participants age, sex and education.
Participants completed two consecutive nights of polysomnography (a recording of changes that occur in the brain during sleep) while sleeping in a laboratory, and 12 hours later underwent magnetic resonance image (MRI) scanning while completing a cognitive memory test, called the N-back task (commonly used as an assessment in cognitive neuroscience to measure a part of working memory, similar to testing concentration).
They then completed a series of other tests including a sleep questionnaire and a series of questions about motivation to perform well, amount of effort required to perform the task and perceived speech difficulty.
The researchers compared the findings between people with primary insomnia and good sleepers.
What were the basic results?
People with insomnia showed similar performance compared to good sleepers on all measures and on all levels of difficulty for the memory and concentration testing (N-back task) at the start of the study, i.e. they were similar before their sleep.
At 12 hours, when they underwent functional magnetic resonance image (MRI) scanning while doing the N-back memory and concentration test they found different areas of the brain were more active and others less active.
People with primary insomnia showed reduced activation of task-related working memory regions compared to good sleepers. When people were given this task, certain parts of the brain became less active (‘deactivation’), however this didn’t happen as much among people with insomnia.
This ‘deactivation’ in certain parts of the brain is said to happen when attention is diverted to task-related behaviour (such as the N-back task). This triggers activity in other parts of the brain.
How did the researchers interpret the results?
One of the researchers, Professor Sean Drummond is reported as saying: “We found that insomnia subjects did not properly turn on brain regions critical to a working memory task and did not turn off ‘mind-wandering’ brain regions irrelevant to the task”.
He is also reported as saying: “This data helps us understand that people with insomnia not only have trouble sleeping at night, but their brains are not functioning as efficiently during the day.”
This study looked at differences in brain activity assessed on MRI between people with and without insomnia while they completed a memory task of increasing difficulty. This is a relatively small study, with only 50 participants who were on average 32-years-old. Larger studies including participants of different ages are needed to draw firmer conclusions about differences in brain activity during these tasks.
There are some other limitations worth noting:
- only people with primary insomnia who did not have any other psychiatric conditions were included. The researchers say it would be useful for future research in this area to include people with insomnia who have other psychiatric conditions due to the prevalence of these conditions together
- people with insomnia included in the study on average had moderate severity of insomnia. Only three of 25 participants scored in the severe insomnia range, so findings from this study may not be applicable to people with severe insomnia
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.