Association Between Time Spent Outdoors and Risk of Multiple Sclerosis, 2022, Sebastian et al.

Association Between Time Spent Outdoors and Risk of Multiple Sclerosis
Prince Sebastian; Nicolas Cherbuin; Lisa F. Barcellos; Shelly Roalstad; Charles Casper; Janace Hart; Gregory S. Aaen; Lauren Krupp; Leslie Benson; Mark Gorman; Meghan Candee; Tanuja Chitnis; Manu Goyal; Benjamin Greenberg; Soe Mar; Moses Rodriguez; Jennifer Rubin; Teri Schreiner; Amy Waldman; Bianca Weinstock-Guttman; Jennifer Graves; Emmanuelle Waubant; Robyn Lucas; on behalf of US Network of Pediatric Multiple Sclerosis Centers

Background and Objectives
This study aims to determine the contributions of sun exposure and ultraviolet radiation (UVR) exposure to risk of pediatric-onset multiple sclerosis (MS).

Methods
Children with MS and controls recruited from multiple centers in the United States were matched on sex and age. Multivariable conditional logistic regression was used to investigate the association of time spent outdoors daily in summer, use of sun protection, and ambient summer UVR dose in the year before birth and the year before diagnosis with MS risk, with adjustment for sex, age, race, birth season, child's skin color, mother's education, tobacco smoke exposure, being overweight, and Epstein-Barr virus infection.

Results
Three hundred thirty-two children with MS (median disease duration 7.3 months) and 534 controls were included after matching on sex and age. In a fully adjusted model, compared to spending <30 minutes outdoors daily during the most recent summer, greater time spent outdoors was associated with a marked reduction in the odds of developing MS, with evidence of dose-response (30 minutes–1 hour: adjusted odds ratio [AOR] 0.48, 95% confidence interval [CI] 0.23–0.99, p = 0.05; 1–2 hours: AOR 0.19, 95% CI 0.09–0.40, p < 0.001). Higher summer ambient UVR dose was also protective for MS (AOR 0.76 per 1 kJ/m2, 95% CI 0.62–0.94, p = 0.01).

Discussion
If this is a causal association, spending more time in the sun during summer may be strongly protective against developing pediatric MS, as well as residing in a sunnier location.

Link | PDF (Neurology)

 

(I wonder if vitamin D levels is a proxy and that UV radiation exposure is not the key factor, but instead near-infrared.)

 

There was a graph I saw in a paper years ago which plotted ms incidence rates v location . There was a definite relationship - the farther from the equator the higher the incidence , suggesting sunlight exposure plays a part. It's always assumed as being vit D related , but infrared radiation is interesting.

 

Yes the latitude relationship is well established. An interesting feature is that early life exposure appears to be key, ie if you moved to a lower latitude after 12yo you carried your higher risk, or vice versa.

See The latitude gradient for multiple sclerosis prevalence is established in the early life course (2021, Brain) from some of my local colleagues.

 

Vitamin D did not reduce multiple sclerosis disease activity after a clinically isolated syndrome, 2023, Helmut Butzkueven et al

https://academic.oup.com/brain/advance-article/doi/10.1093/brain/awad409/7469896?login=false

 

Canada continues to have the highest rates of MS in the world.

• Over 90,000 Canadians living with MS – 1 in every 400
• 4,377 people are diagnosed with MS each year - almost 12 people per day
• Average age of diagnosis is 43 years
• 75% of the people living with MS are women
• 90% of people with MS are initially diagnosed with relapsing-remitting forms of MS, while 10% are diagnosed with progressive forms of MS.

https://mscanada.ca/ms-research/latest-research/prevalence-and-incidence-of-ms-in-canada-and-around-the-world#:~:text=Canada continues to have one,MS – 1 in every 400