Maintaining good physical fitness and regularly engaging in moderate-intensity exercise may be linked to a lower risk of developing amyotrophic lateral sclerosis (ALS) in adulthood, according to a new study just published in the American Academy of Neurology’s journal Neurology, which found this association only in male participants, not in women.
Amyotrophic lateral sclerosis is a rare, progressive neurodegenerative disease that affects nerve cells in the brain and spinal cord. People with ALS lose the ability to initiate and control muscle movements, which usually leads to complete paralysis and death. The average life expectancy after diagnosis is two to five years, so identifying factors that help prevent or delay its appearance is key.
The study’s authors analysed 373,696 people living in Norway with an average age of 41 years, who were followed for an average of 27 years. Among all participants, 504 people developed ALS, of whom 59% were men.
Participants recorded their physical activity level over the past year in one of four categories: sedentary; at least four hours of walking or cycling per week; at least four hours a week of recreational sports or intense gardening; or rigorous training or sports competitions several times a week. Due to the small number of participants in the highest level of physical activity, the researchers combined categories three and four into a single high-activity group.
Up to 41% lower risk of ALS based on physical activity
The researchers found that of the 41,898 men with the highest level of physical activity, 63 developed ALS; Of the 76,769 men with an intermediate level of physical activity, 131 developed ALS; and of the 29,468 men with the lowest level of physical activity, 68 developed ALS.
After adjusting for other factors that could affect ALS risk, such as smoking and body mass index, the researchers found that men with moderate levels of physical activity had a 29% lower risk of developing ALS compared to those with the lowest level of physical activity. Those who had high levels of physical activity had a 41% lower risk.
In the case of men, “moderate to high levels of activity and physical fitness not only do not increase the risk of ALS, but may have a protective effect against the disease”
The researchers also looked at resting heart rate. Men in the lowest resting heart rate category, which indicates good fitness, had a 32% lower risk of developing ALS compared with those with higher heart rates.
“Our findings show that, for men, moderate to high levels of activity and fitness not only do not increase the risk of ALS, but may have a protective effect against the disease,” said Dr. Anders Myhre Vaage of the Akershus University Hospital in Norway and lead author of the study. “Future studies on the connection between ALS and exercise should consider sex differences and higher or professional levels of physical activity.”
One limitation of this research that its authors have acknowledged is that the physical activity questionnaire was completed only at one specific time during the study, so it may not have reflected participants’ exercise levels over the nearly 30 years of follow-up.
