Athleticism increases disease risk

Slim people seem to be more at risk

People with motor neurone disease are significantly more likely to have been slim and athletic, research suggests.

A form of motor neurone disease called Amyotrophic Lateral Sclerosis has been associated with many patients who were lean and athletic throughout their lives.

In fact, ALS is also known as Lou Gehrig's Disease, after the great New York Yankees baseball player whose career was cut short by the disease.

Scientists from Columbia University in New York investigated whether the anecdotal evidence of a link to body size could be backed up by hard data.

Lou Gehrig's career and life were cut short

They compared details of 279 patients with motor neurone disease with 152 patients with other neurological conditions.

The odds of having motor neurone disease were 2.21 times higher in subjects who had always been slim, and 1.70 times higher among people who had played sport at university representative level.

It is not known what contributes to the higher concentration of motor neurone disease in top athletes.

Researchers have put forward a number of theories for the impact of vigorous physical activity:

• it increases exposure to environmental toxins
• it speeds up the transport of toxins to the brain
• it increases the absorption of toxins
• it increases the athlete's susceptibility to motor neurone disease through added physical stress

Researcher Dr Lewis Rowland said more could be learned in follow-up studies that look in-depth at the nature of the activity, the environmental setting, and the intensity.

He said: "Thousands and thousands of slim athletes never develop ALS.

"Why a tiny few of them do is unknown. We do know that there is no justification to avoid athletics in an attempt to avoid motor neurone diseases."

Best research

Dr Brian Dickie, Director of Research Development at the Motor Neurone Disease Association, said: "It has long been suspected that athletic individuals are more susceptible to develop motor neurone diseases in later life, but this is the best evidence to date.

"It should be emphasised that a two-fold increase in the likelihood of developing MND still means that the chances of an individual developing the disease remain very slim.

"It does raise the theories as to why this should be the case and will doubtless provide the impetus for further research to try and determine the physiological mechanisms underlying motor neuron vulnerability."

The study is published in Neurology, the journal of the American Academy of Neurology.