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.
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, told this news organization.
“I hadn’t really expected that, but those results were quite strong, even stronger than sleep duration,” Dr. 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 in the Journal of Neurology, Neurosurgery and Psychiatry.
Strong association
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 Dr. 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 2,075 patients with MS and 3,164 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% confidence interval [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 adjustment 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, Dr. 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,” Dr. 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 Dr. 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.