By Owen Dyer (London)
US veterans of the 1991 Persian Gulf war are twice as likely as the general public to develop amyotrophic lateral sclerosis (ALS), a type of motor neuron disease. This is a finding of two studies published in the current issue of the journal Neurology ( 2003; 61: 742-9, 750-6).
The condition, known in the United States as Lou Gehrig's disease (after the baseball player who was the most famous person to have developed it), remains extremely rare among Gulf war veterans, but the rate of diagnosis has been climbing faster in recent years, suggesting a delayed effect that may become more apparent over time.
The first of the two studies, which was sponsored by the US Department of Veterans' Affairs, compared rates of amyotrophic lateral sclerosis in service personnel deployed to south west Asia with rates of the disease among those who were not deployed there.
The researchers verified 107 cases of amyotrophic lateral sclerosis, of which 40 came from the deployed population of 696 118 and 67 came from the non-deployed population of 1 786 215. This would suggest almost a doubling of risk among soldiers who were deployed, the authors said. The risk appeared to be highest for air force veterans (relative risk 2.68, 95% confidence interval 1.24 to 5.78), followed by army veterans (2.04, 1.10 to 3.77).
One of the authors, Ronnie Horner of the National Institute of Neurological Disorders and Stroke, said: "This study addressed the question, 'Is there a problem with excessive occurrence of ALS among Gulf war veterans?' We found the answer to be yes."
The studies seem to confirm earlier findings that two years ago led the Veterans' Affairs Department to list the disease as a service related condition covered by full disability benefits. But an accompanying editorial in Neurology (pp 730-1), by Michael Rose of King's College Hospital, London, warned that with such a rare condition the sample sizes are too small to be relied on for evidence.
"While a twofold increase in risk may seem impressive, one needs to realize that this is based upon just a small number of cases," he wrote. "Therefore the calculated risk may easily be changed either way if the methodology has any flaws."
Source: BMJ 2003;327:766 (4 October). Online at www.bmj.com.