A new study published in the Journal of Neurology Neurosurgery & Psychiatry reveals evidence of a link between physical activity and amyotrophic lateral sclerosis (ALS), supporting the idea that a history of vigorous exercise may increase the risk of developing this rare neurological disorder.
ALS, also known as Lou Gehrig’s disease , primarily attacks motor nerve cells, or neurons, that regulate the muscles behind voluntary movements, such as walking, talking, and chewing.
The research, conducted by members of a large European project studying ALS, examined subjects in Ireland, Italy and the Netherlands. And it is important to note that experts do not advocate reducing physical activity, as physical activity has been shown to protect against health problems that are much more common than ALS, such as diabetes, various cancers and cardiovascular diseases.
Possible causes
This rare disorder begins to present with stiffness and weakness in the muscles, but gradually progresses to the point where the brain can no longer control voluntary movement and patients lose the ability to eat, speak, move, and eventually breathe.
The exact cause of ALS and why it affects some groups of people more than others is still unknown. However, the evidence suggests that genes and the environment (exposure to toxic chemicals, diet, physical trauma …) are involved.
The link with physical activity emerged from a few individual case studies; the most famous was that of the American baseball player Lou Gehrig, hence the disease also bears his name. But the evidence linking physical activity to ALS has not been conclusive, and the authors of the new paper suggest that the main reason is that the studies have been set up differently and used different methods.
For their research, the scientists analyzed data on subjects recruited for a “case-control study” that was carried out by the EURO-MOTOR project that compiles a “robust and validated computerized ALS model” by generating ” large-scale quantitative data sets “.
The data come from validated questionnaires completed by 1,557 adults who had just been diagnosed with ALS, and 2,922 people without the disease as control subjects . The participants, who lived in Ireland, Italy and the Netherlands, were matched for age, sex and place of residence and were over 60 years old.
Using the data that each subject gave on the amount of time per week spent on each activity and how many years that activity lasted, and referring to a compendium that provides MET scores for different activities, the scientists calculated a lifetime score of physical activity for each person.
Analysis of the full set of cases showed that lifetime physical activity during work hours was associated with a 7% increased risk of ALS and a 6% increased risk with leisure time physical activity.
The combination of both exercises (at work and at leisure) gave an overall risk increase of 6% . The overall risk for all physical activities translated into a 26% higher risk of developing ALS in the subjects who had the highest lifetime scores compared to those who had the lowest, supporting the idea that the ALS is more common in athletes and professional athletes.
The authors note that due to the observational nature of their study, their findings do not prove that vigorous physical activity actually causes ALS. Other factors, such as a metabolic or energy disorder, or even trauma or diet, “cannot be ruled out.”
“However, the data is intriguing and warrants further investigation on a case-by-case basis,” explains Michael Swash, leader of the work.
Reference: Multicentre, cross-cultural, population-based, case – control study of physical activity as risk factor for amyotrophic lateral sclerosis. Journal of Neurology Neurosurgery & Psychiatry 2018 DOI: http://dx.doi.org/10.1136/jnnp-2017-317724
