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Published online: 2 April 2007; | doi:10.1038/news070402-1
Link suggested between soccer and motor neurone diseaseExperts call for investigation into sport and fatal brain condition.Michael Hopkin 
| Kick it: repeated heading of the ball might harm the brain. Getty |
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British
neuroscientists are planning to investigate whether playing soccer
contributes to the development of motor neurone disease. The move comes
after three amateur footballers playing in the same league developed
the disease, which normally affects less than one person in every
50,000 each year.
Experts
are now aiming to launch a full epidemiological study of professional
footballers and motor neurone disease (MND) patients, to see whether
the sport really does raise the incidence of the disease among those
who play it at a high level.
Details of the patients, all of whom were committed footballers, are published in the journal Amyotrophic Lateral Sclerosis1
— a publication named after the most common form of MND. The patients
range in age between 56 and 61 years old, and were all diagnosed with
the disease within a decade of each other.
"What
is unusual about this group is that they are all friends who developed
MND at the same time," says Ammar Al-Chalabi of King's College London,
one of the experts who described the cases. "A cluster like this could
occur by chance, but the odds are quite long."
The
three have several potential risk factors in common, including having
been electrocuted by mains electricity at some point during their
lives. But the authors note that the three were very keen at football,
playing more than twice a week — almost as much as professional players.
"The
next step is a proper epidemiological study," Al-Chalabi adds. He and
his colleagues are planning to approach the Professional Footballers'
Association to request data on former professional footballers, to see
whether they have a higher than normal incidence of the disease.
Blows to the head
A
possible link between football and MND, which causes paralysis and is
ultimately fatal, has been found before. In 2005, Italian researchers
reported that professional footballers playing in that country between
1970 and 2001 were more than six times more likely to have developed
the condition2. These findings were a by-product of a study looking for evidence of past steroid abuse among footballers.
 Don't let this stop you playing football  |
Brian Dickie, Motor Neurone Disease Association.
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MND
has a wealth of possible causes, including genetic factors. The most
obvious suggestion in the case of soccer players is that repeated
heading of the ball might harm the brain. Many boxers, most notably
Muhammad Ali, who now suffers from a form of Parkinson's, have suffered
brain diseases as a result of repeated blows to the head.
But
two of the three English patients say they avoided heading the ball
during play. And MND involves the death of motor neurons, most of which
are deep in the brain and spinal cord, and would therefore be less
likely to be damaged by impacts to the skull.
Another
theory is that harmful pesticides on the grass, or compounds in the
paint used to mark the pitch, might find their way into the bloodstream
through minor grazes or even directly through the skin when the ball
hits it, Al-Chalabi and his colleagues suggest. It is clear that some
chemicals can kill nerve cells, although there is no established link
to MND.
Yet
another possibility is that the frequent high activity of motor neurons
in sportspeople may generate large amounts of chemical waste products
that damage nerve cells, leading to an increased likelihood of
developing MND later in life.
Keep on playing
"Basically,
all theories are valid at the moment. That's part of the problem,"
comments Brian Dickie, director of research development at the Motor
Neurone Disease Association.
Dickie
says that "it's worth seeing if the Italian study could be replicated"
in a study intended to look for a link between football and MND. He is
currently spearheading the creation of a database of 1,500 MND patients
and 1,500 carefully matched control volunteers, in a bid to tease out
some of the causes of this rare condition.
Meanwhile,
Dickie is at pains to point out that the health benefits of sport far
outweigh the possible negatives. "Don't let this stop you playing
football," he urges. "The Italians had a sixfold increase in likelihood
of MND. That sounds like a lot but a sixfold increase in a rare disease
still means it's a rare disease."
References
- Wicks P., et al. Amyotrophic Lateral Sclerosis, doi: 10.1080/17482960701195220 (2007).
- Chio A., Benzi G., Dossena M., Mutani R. & Mora G. Brain, 128
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451
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453
(2005).
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