Sweden Study: Sleep and Multiple Sclerosis

A recent case-control study has found that low sleep quality and insufficient sleep during the teenage years increase the risk of subsequent development of multiple sclerosis (MS). The study's findings appeared in the Journal of Neurology Neurosurgery & Psychiatry.

The researchers suggest that sufficient restorative sleep while young, needed for proper immune functioning, may help to prevent multiple sclerosis.

Factors Influencing MS

MS is influenced by both genetic and environmental factors, including:

• Smoking
• Teenage weight (BMI)
• Epstein-Barr virus infection
• Sun exposure
• Vitamin D

Shift work has also been linked to a heightened risk of the condition, particularly at a young age. Still, they add that whether sleep patterns-duration, body clock disruption, and sleep quality might affect this risk hasn’t been fully assessed.

The Study

To explore this further, the researchers drew on a population-based case-control study, the Epidemiological Investigation of Multiple Sclerosis (EIMS), comprising 16–70-year-old Swedish residents.

People with MS were recruited from hospitals and privately run neurology clinics and matched for age, sex, and residential area with two healthy people randomly selected from the national population register between 2005 and 2013 and 2015 and 2018.

The researchers focused particularly on sleep patterns from 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: length of sleep on work or school days and at weekends or on free days.

• Short sleep was defined as less than 7 hours/night
• Adequate sleep as 7–9 hours
• Long sleep as ten or more hours

Changes in sleep timing between work/school days and weekend/free days were calculated during the teen years of 15-19 and categorised as:

• Less than 1 hour/night
• 1-3 hours
• More than 3 hours

Study participants were also asked to assess sleep quality during different age periods using a 5-point scale, where 5 equals very good.

Findings

The average age at which MS was diagnosed was 34. Sleep length and quality during adolescence were associated with the risk of an MS diagnosis, which increased in tandem with fewer hours of, and poorer quality, sleep.

Compared with sleeping 7–9 hours/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. But long sleep, including at weekends or on free days, wasn’t associated with a heightened MS risk.

Similarly, subjectively assessed poor sleep quality during this period was associated with a 50% heightened risk of developing the condition.

Changes in sleep timing between work/school days and weekends/free days didn’t seem influential. The findings remained similar when those who worked shifts were excluded.

Conclusions

The researchers caution that their findings should be interpreted cautiously on account of potential reverse causation—whereby poor sleep could be a consequence of neurological damage rather than the other way round.

But they point out that too little and poor sleep quality affects immune pathways and inflammatory signalling. At the same time, the body clock is also involved in regulating the immune response.

And insufficient or disturbed sleep is common among teens, a phenomenon partly explained by physiological, psychological, and social changes during this age period, they explain.

“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 add.

“Educational interventions addressed to adolescents, and their parents regarding the negative health consequences of insufficient sleep are of importance.”

And 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.”

Reference

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 Published Online First: 23 January 2023. doi: 10.1136/jnnp-2022-330123