Too little sleep or poor sleep quality during the teen years can significantly increase the risk for multiple sclerosis (MS) during adulthood, new research suggests.
In a large case-control study, individuals who slept less than 7 hours a night on average during adolescence were 40% more likely to develop MS later on. The risk was even higher for those who rated their sleep quality as bad.
On the other hand, MS was significantly less common among individuals who slept longer as teens ― indicating a possible protective benefit.
Dr Torbjörn Åkerstedt
While sleep duration has been associated with mortality or disease risk for other conditions, sleep quality usually has little to no effect on risk, lead investigator Torbjörn Åkerstedt, PhD, sleep researcher and professor of psychology, Department of Neuroscience, Karolinska Institutet, Stockholm, Sweden, told Medscape Medical News.
“I hadn’t really expected that, but those results were quite strong, even stronger than sleep duration,” Åkerstedt said.
“We don’t really know why this is happening in young age, but the most suitable explanation is that the brain in still developing quite a bit, and you’re interfering with it,” he added.
The findings were published online January 23 in the Journal of Neurology, Neurosurgery and Psychiatry.
Other studies have tied sleep deprivation to increased risk for serious illness, but the link between sleep and MS risk isn’t as well studied.
Previous research by Åkerstedt showed that the risk for MS was higher among individuals who took part in shift work before the age of 20. However, the impact of sleep duration or quality among teens was unknown.
The current Swedish population-based case-control study included 2075 patients with MS and 3164 without the disorder. All participants were asked to recall how many hours on average they slept per night between the ages of 15 and 19 years and to rate their sleep quality during that time.
Results showed that individuals who slept fewer than 7 hours a night during their teen years were 40% more likely to have MS as adults (odds ratio [OR], 1.4; 95% CI, 1.1 – 1.7).
Poor sleep quality increased MS risk even more (OR, 1.5; 95% CI, 1.3 – 1.9).
The association remained strong even after adjusting for additional sleep on weekends and breaks and excluding shift workers.
Long Sleep “Apparently Good”
The researchers also conducted several sensitivity studies to rule out confounders that might bias the association, such as excluding participants who reported currently experiencing less sleep or poor sleep.
“You would expect that people who are suffering from sleep problems today would be the people who reported sleep problems during their youth,” but that didn’t happen, Åkerstedt noted.
The investigators also entered data on sleep duration and sleep quality at the same time, thinking the data would cancel each other out. However, the association remained the same.
“Quite often you see that sleep duration would eliminate the effect of sleep complaints in the prediction of disease, but here both remain significant when they are entered at the same time,” Åkerstedt said. “You get the feeling that this might mean they act together to produce results,” he added.
“One other thing that surprised me is that long sleep was apparently good,” said Åkerstedt.
The investigators have conducted several studies on sleep duration and mortality. In recent research, they found that both short sleep and long sleep predicted mortality ― “and often, long sleep is a stronger predictor than short sleep,” he said.
Commenting on the findings for Medscape Medical News, Kathleen Zackowski, PhD, associate vice president of research for the National Multiple Sclerosis Society in Baltimore, Maryland, noted that participants were asked to rate their own sleep quality during adolescence, a subjective report that may mean sleep quality has an even larger association with MS risk.
“That they found a result with sleep quality says to me that there probably is a bigger problem, because I don’t know if people over- or underestimate their sleep quality,” said Zackowski, who was not involved with the research.
“If we could get to that sleep quality question a little more objectively, I bet that we’d find there’s a lot more to the story,” she said.
That’s a story the researchers would like to explore, Åkerstedt reported. Designing a prospective study that more closely tracks sleeping habits during adolescence and follows individuals through adulthood could provide valuable information about how sleep quality and duration affect immune system development and MS risk, he said.
Zackowski said clinicians know that MS is not caused just by a genetic abnormality and that other environmental lifestyle factors seem to play a part.
“If we find out that sleep is one of those lifestyle factors, this is very changeable,” she added.
The study was funded by the Swedish Research Council, the Swedish Research Council for Health, Working Life and Welfare, the Swedish Brain Foundation, AFA Insurance, the European Aviation Safety Authority, the Tercentenary Fund of the Bank of Sweden, the Margaretha af Ugglas Foundation, the Swedish Foundation for MS Research, and NEURO Sweden. Akerstadt has been supported by Tercentenary Fund of Bank of Sweden, AFA Insurance, and the European Aviation Safety Authority. Zackowski reports no relevant financial relationships.
J Neurol Neurosurg Psychiatry. Published online January 23, 2023. Full text
Kelli Whitlock Burton is a reporter for Medscape Medical News covering neurology and psychiatry.
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