Some researchers have theorized that regular physical activity reduces the risk of developing multiple sclerosis. A new analysis demonstrates that, as a preventative measure, exercise does not appear to have the desired effect.
MS is a varied condition that affects the brain and/or spinal cord.
It can cause a wide range of symptoms including difficulties with the movement of limbs, changes in vision, and problems with balance and sensation.
Although there is no cure, scientists have demonstrated that, for individuals with mild to moderate disability, exercise can improve the severity of certain symptoms.
Exercise has been shown to increase muscular strength and aerobic capacity and improve the individual's sense of wellness. Additionally, there is some evidence that exercise might help slow the progression of MS, although the data is conflicting.
How exercise reduces the symptoms of MS is not known, but researchers believe that it could be due to the modulation of immune factors or stress hormones, or perhaps by altering the expression of neuronal growth factors.
Risk factors for MS
A number of MS risk factors are known; for instance, the condition is more prevalent in women than men, and it seems to have links with certain infections, including Epstein-Barr. White people and those who live in temperate climates are also more likely to develop MS. However, the full list of risks is yet to be uncovered.
One potential risk factor that has received some attention from scientists is the level of exercise an individual is involved in prior to the onset of MS. It is commonly believed that a higher level of physical activity reduces the risk of MS; however, this is still very much up for debate.
Findings are contradictory or unclear; for instance, some studies have shown that individuals who develop MS tend to be more physically active before onset; others showed no difference in pre-onset activity.
However, earlier studies did not use detailed, validated questionnaires to assess physical activity levels. There is also a confounding variable that makes some of the results difficult to interpret. Two of the early symptoms of MS are weakness and fatigue. So, did the lack of physical exercise promote the onset of MS, or was the lack of exercise a sign of the onset of MS?
A team of scientists from Harvard T.H. Chan School of Public Health in Boston, MA, recently set out to investigate whether physical activity has an effect on MS risk once and for all. Their results are published this week in the journal Neurology.
Fitness level and the onset of MS
The team took data from more than 193,000 women who participated in the Nurses' Health Study and Nurses' Health Study II; these individuals were followed up for 20 years, starting in 1976. Each woman completed detailed questionnaires about their current levels of physical activity and also their activity levels as teens and young girls. Over the course of 20 years, 341 women developed MS.
Once the data were collated, the researchers calculated the hours of exercise each individual carried out per week and what types of exercise they did. The group adjusted the results for ethnicity, age, smoking, place of residence at the age of 15, BMI at 18, and vitamin D supplement intake.
After the analysis had been completed, the data showed that, contrary to expectation, exercise was not correlated in any way to the appearance of MS.
"Overall, there was no consistent association of exercise at any age and MS. Exercise has been shown to be beneficial to people with the disease, but it seems unlikely that exercise protects against the risk of developing MS."
Kassandra Munger, study author
When Medical News Today asked Munger whether the results had come as a surprise, she said:
"Given the overall health benefits of physical activity, in addition to recent studies suggesting that physical activity in persons with MS may provide some benefit, our working hypothesis was that physical activity would be associated with a reduced MS risk."
Although the team has no further MS studies planned at this stage, in a perfect future, Munger told MNT that she would "spend time and money on better understanding the role for physical activity in promoting wellness and improving quality of life among MS patients."
We still have much to learn about MS and the risk factors involved. No doubt further research will steadily provide the vital details necessary to prevent this debilitating condition.