More physical activity tied to lower MS risk with low sun exposure
Researchers say the subgroup finding is exploratory and needs confirmation
Written by |
Higher physical activity was linked to lower MS risk mainly among people with low sun exposure in a Swedish study. (Image from iStock)
- Higher physical activity was linked to lower odds of multiple sclerosis mainly among people with low sun exposure.
- No clear overall association remained between physical activity and multiple sclerosis after accounting for lifestyle and environmental factors.
- In assessing the link between physical activity and MS risk, researchers say sun exposure, outdoor activity, and broader lifestyle patterns should also be considered.
Higher levels of physical activity may be associated with a lower likelihood of developing multiple sclerosis (MS), mainly among people with low sun exposure, a Swedish study suggests.
The study assessed leisure-time physical activity and sun exposure. In the overall population, no clear overall association was found between physical activity and MS risk after accounting for other lifestyle and environmental factors.
According to the researchers, these findings suggest that the association between physical activity and MS risk may vary with sun exposure, highlighting “the importance of considering physical activity in relation to sun exposure, outdoor activity, and broader lifestyle patterns.”
The study, “Leisure-time physical activity, sun exposure, and multiple sclerosis risk: a population-based case–control study,” was published in the Journal of Neurology.
Physical activity’s role in MS risk remains unclear
Several genetic and environmental factors are known to influence a person’s risk of developing MS, but evidence for the role of physical activity is less clear. One reason is that physical activity is closely linked with other lifestyle and environmental factors, including sun exposure, making their individual effects difficult to separate.
To investigate further, researchers in Sweden set out to assess whether leisure-time physical activity was associated with MS risk, while also considering sun exposure and other environmental factors.
The study included 3,008 people with MS and 5,773 controls matched based on sex, age, and residential area. At enrollment, participants were asked about what their leisure-time physical activity had been five years earlier. If their activity varied by season, they reported an average across that year. The sun-exposure questions covered the entire five years before enrollment. Sun exposure was evaluated through a questionnaire assessing sunbathing, travel to sunnier countries, and use of sunbeds. Sun exposure scores averaged 6.2 among people with MS and 6.5 among controls; in the main analysis, scores of 6 or higher were classified as high sun exposure.
In an initial analysis taking into account age, sex, and residential area, higher levels of physical activity were significantly associated with a lower risk of MS. However, the association weakened, and no clear overall link remained after adjusting for additional factors, including educational level, ancestry, smoking status, alcohol consumption, body mass index (a proxy for body fat based on height and weight), and sun exposure.
Lower MS odds seen with higher activity and low sun exposure
Because the researchers found that sun exposure appeared to influence the association between physical activity and MS risk, they analyzed participants according to their level of sun exposure. Among those with low sun exposure, participants with the highest level of physical activity had 24% lower odds of MS than those with the lowest level, even after accounting for the other factors.
Among participants with information on time spent outdoors, higher physical activity remained associated with lower odds of MS after researchers adjusted for outdoor activity. In the main analysis, no similar association was seen among people with high sun exposure.
“In conclusion, leisure-time physical activity was not clearly associated with MS risk in the overall multivariable analysis, but an inverse association was observed among individuals with low sun exposure and in sensitivity analyses with adjustment for outdoor activity,” the researchers wrote.
“This pattern suggests that the association between physical activity and MS risk may vary according to sun exposure, although the findings require cautious interpretation,” they added.
The researchers said the finding involving sun exposure requires replication. They also noted that early MS-related changes could affect physical activity before clinical symptoms appear, making it difficult to determine whether physical activity itself influences MS risk.
Leave a comment
Fill in the required fields to post. Your email address will not be published.