Regular, strenuous exercise increases the risk of motor neuron disease (MND) in people who are genetically predisposed to the condition, researchers say.
Scientist University of Sheffield found a causal relationship between high-intensity physical activity and disorders in people who were already at risk of disease.
They believe this work will be an important step in understanding the relationship between high intensity exercise, which can cause motor nerve damage in some people, and the neurodegenerative disease that affects approximately 5,000 people in the UK.
“We have suspected that exercise is a risk factor for MND for some time, but until now this association has been considered controversial,” said Dr. Jonathan Cooper-Knock, a neurologist in Sheffield. “This study confirms that in some people, repetitive strenuous exercise increases the risk of MND.”
The lifetime risk of developing MND is around 1 in 400, but previous studies have shown it is six times higher in professional soccer players than in the general population. A number of notable British athletes have shared their experiences with MND in recent years, including Rob Burrow of the Rugby League, Doddie Weir of the Rugby Union and footballer Stephen Darby.
The Sheffield researchers emphasize that the vast majority of people who exercise intensely will not develop MND and that their next step is to develop tests that will identify those most at risk.
Writing in the magazine EBioMedicineThe scientists described how they analyzed data from the UK Biobank project, which contains detailed information about the genes and lifestyles of half a million people. They found that people with a genetic makeup that made them more likely to do strenuous exercise were also more likely to develop MND.
With vigorous exercise, the activity levels of several genes associated with the disease changed, while people with a mutation that makes up 10% of MND developed the disease earlier if they participated in regular high-intensity exercise.
Professor Dame Pamela Shaw, Director of the Sheffield Institute of Neuroscience, said, “It is clear that most people who do strenuous exercise do not develop motor nerve injury and more work is required to identify the exact genetic risk factors.”
“The ultimate goal is to identify environmental risk factors that may predispose to MND in order to educate disease prevention and lifestyle decisions.”
MND, also known as amyotrophic lateral sclerosis, affects nerves in the brain and spinal cord. As the disease progresses, the messages from the nerves are interrupted and eventually fail to reach the muscles, causing them to stiffen and shrink. The disease can seriously affect people’s ability to move their limbs, speak, eat, and breathe. While about 10% of cases are inherited, the rest are caused by a complex interaction between genes and the environment.