Teenagers who do not get enough sleep could increase their risk of multiple sclerosis (MS) in later life, a new Swedish study suggests today.
Although it is known that MS is influenced by both genetic and environmental factors, and shift work has also been linked to a heightened risk, sleep patterns have not been fully assessed, the researchers say.
A team from the Department of Clinical Neuroscience at the Karolinska Institutet, used data from the Epidemiological Investigation of Multiple Sclerosis (EIMS), a population-based case-control study, comprising Swedish residents aged 16 to 70.
People with MS were recruited from hospital and privately run neurology clinics and matched for age, sex, and residential area with two healthy people who were randomly selected from the national population register between 2005 and 2013 and 2015 and 2018.
The researchers focused particularly on sleep patterns during the ages 15 to 19, and the final analysis included 2075 people with MS and 3164 without the condition in this age group when recruited to the study.
Participants were asked about their sleeping patterns at different ages, such as length of sleep on work or school days, and at weekends or on free days.
Short sleep was defined as seven hours or under a night, while adequate was categorised as seven to nine hours. Long sleep was 10 or more hours.
Changes in sleep timing between work and school days and weekend and free days were calculated during 15-19 years and were categorised as less than one hour a night, one to three hours, and more than three hours.
Study participants were also asked to assess sleep quality during different age periods using a five-point scale, where five was “very good”.
Writing in *Journal of Neurology Neurosurgery & Psychiatry*, the team says the average age at which MS was diagnosed was 34.
Compared with sleeping seven to nine hours a night during the teenage years, short sleep was associated with a 40% heightened risk of subsequently developing MS, after accounting for a range of potentially influential factors, including BMI at age 20 and smoking.
However, long sleep, including at weekends or on free days, was not associated with a heightened MS risk.
Poor sleep quality during this period was associated with a 50% heightened risk of developing the condition and the findings were similar when those who worked shifts were excluded.
The researchers say although their findings should be interpreted cautiously because of potential reverse causation, they add that too little and poor sleep quality is known to affect immune pathways and inflammatory signalling, while the body clock is also involved in regulating the immune response.
They also point out a lack of or disturbed sleep is common among teenagers, a phenomenon that is partly explained by physiological, psychological, and social changes.
“Associations have also been demonstrated between social media use and sleep patterns. Availability of technology and internet access at any time contributes to insufficient sleep among adolescents and represents an important public health issue,” they write.
“Educational interventions addressed to adolescents and their parents regarding the negative health consequences of insufficient sleep are of importance.”
They conclude: “Insufficient sleep and low sleep quality during adolescence seem to increase the risk of subsequently developing MS. Sufficient restorative sleep, needed for adequate immune functioning, may thus be another preventive factor against MS.”
Åkerstedt T, Olsson T, Alfredsson L et al. Insufficient sleep during adolescence and risk of multiple sclerosis: results from a Swedish case control study. *Journal of Neurology Neurosurgery & Psychiatry* 24 January 2023; doi 10.1136/jnnp-2022-330123
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