Regular strenuous exercise raises the risk of developing motor neurone disease (MND) in people who are genetically predisposed to the condition, researchers say.
Scientists at the University of Sheffield found a causal relationship between high intensity physical activity and the disorder among those already susceptible to the disease.
They believe the work marks a major step towards understanding the link between intense exercise, which may contribute to motor neurone injury in certain people, and the neurodegenerative disease, which affects about 5,000 individuals in the UK.
“We have suspected for some time that exercise was a risk factor for MND, but until now this link was considered controversial,” said Dr Johnathan Cooper-Knoc, a neurologist at Sheffield. “This study confirms that in some people, frequent strenuous exercise leads to an increase in the risk of MND.”
The life-time risk of developing MND is about 1 在 400, but previous studies have suggested it is six times greater in professional football players compared with the general population. A number of high-profile British sportsmen have shared their experience with MND in recent years, including rugby league’s Rob Burrow, rugby union’s Doddie Weir and the the footballer Stephen Darby.
The Sheffield researchers emphasise that the vast majority of people who undertake vigorous exercise do not develop MND, and that their next step is to develop tests that identify people most at risk.
Writing in the journal EBioMedicine, the scientists described how they analysed data from the UK Biobank project, which holds detailed genetic and lifestyle information on 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 have developed MND.
With vigorous exercise, activity levels changed for many of the genes linked to the condition, while individuals with a mutation that accounts for 10% of MND developed the disease earlier if they took part in regular, high-intensity exercise.
“Clearly, most people who undertake strenuous exercise do not develop motor neurone injury and more work is needed to pin-point the precise genetic risk factors involved,” said Prof Dame Pamela Shaw, director of the Neuroscience Institute at Sheffield.
“The ultimate aim is to identify environmental risk factors which can predispose to MND, to inform prevention of disease and lifestyle choices.”
MND, also known as amyotrophic lateral sclerosis, affects the nerves in the brain and spinal cord. As the disease progresses, messages from the nerves are disrupted and eventually stop reaching muscles, leading them to stiffen and waste. The disease can dramatically impair people’s ability to move their limbs, talk, eat and breathe. While about 10% of cases are inherited, the remainder are caused by a complex interaction between genes and the environment.