In a large prospective study with validated measures of physical activity, researchers found no evidence that exercise reduced a woman’s risk of developing multiple sclerosis (MS). Although physical activity is known to have numerous health benefits, it seems unlikely to protect a person against the likelihood of developing MS, the study concludes.
The study, published in the journal Neurology, is titled “Physical activity and the incidence of multiple sclerosis.”
“We wanted to find out if exercise lowered the risk of developing MS in women,” Kassandra Munger, ScD, with the Harvard T.H. Chan School of Public Health in Boston, said in a news release. “Our study did not provide evidence to support it.”
Clinical research has reported that, among MS patients with mild or moderate disability, exercise improves muscular strength and aerobic capacity, as well as lessens mobility problems and fatigue. Some studies have shown that exercise or physical activity might even slow MS progression, though evidence is inconsistent. Exercise could potentially modify MS disease activity via multiple mechanisms, including modulating immune factors and stress hormones, and mediating the expression of neuronal growth factors.
To examine the association between MS incidence and physical activity in early life and adulthood, researchers gathered data from more than 193,000 women who took part in the Nurses’ Health Study (NHS; a total of 81,723 women between 1986–2004) and Nurses’ Health Study II (NHS II; 111,804 women, 1989–2009). These women were followed for up to 20 years. Each was asked to complete questionnaires about levels of physical exercise, and previous exercise levels in teenage and childhood years.
Over the course of those years, 341 women in the study groups developed MS.
Using the information provided, the research team calculated the total metabolic equivalent hours of physical activity carried out per week by each individual, and what types of exercise were performed. The analysis was adjusted for ethnicity, age, place of residence at the age of 15, smoking, body mass index (BMI) at the age of 18, and vitamin D supplement intake.
Results showed that in NHS and NHS II, higher strenuous activity at ages 18–22 was weakly associated with a decreased MS rate. In NHS II, however, total early life activity (ages 12–22) had no association with MS, leading the researchers to conclude that evidence does not support exercise being related to a lower risk of MS onset.
“Overall, there was no consistent association of exercise at any age and MS,” Munger said. “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.”