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Physical activity may explain vets’ risk for wasting disease

Nov. 10, 2006
Special to World Science  

A U.S. gov­ern­ment re­port has found “lim­ited and sug­ges­tive ev­i­dence” that mil­i­tary ser­v­ice in­creases the risk for the dev­as­tat­ing, grad­u­al­ly par­a­lyz­ing Lou Geh­rig’s dis­ease. 

But hard phys­i­cal ac­tiv­i­ty—rath­er than the serv­ice it­self—might ex­plain the link, the au­thors wrote, in light of some stud­ies sug­gest­ing pro­fes­sion­al ath­letes are al­so at risk.

The de­gen­er­a­tive nerve dis­ease, for­mal­ly known as amy­otro­phic lat­er­al scle­ro­sis, or ALS, af­fects rough­ly one in ten thou­sand Ame­ri­cans. Vic­tims suf­fer a pro­gres­sive break­down of nerve cells that con­trol the mus­cles, even­tu­al­ly caus­ing pa­ral­y­sis and usu­al­ly death. 

The re­port was re­leased Nov. 10 from the In­sti­tute of Med­i­cine, a part of the U.S. Na­tion­al Acad­e­my of Sci­ences.

The ev­i­dence link­ing mil­i­tary serv­ice to the dis­ease “is rath­er sparse, so we could not reach more de­fin­i­tive con­clu­sions at this time,” said Rich­ard T. John­son, a neu­rol­o­gist at Johns Hop­kins Uni­ver­si­ty in Bal­ti­more, Md. and chair­man of the com­mit­tee that wrote the re­port. “Be­cause ALS oc­curs so rare­ly, any in­di­vid­u­al vet­er­an’s chances of de­vel­op­ing the dis­ease are still low.”

More high-quality stud­ies are needed, ac­cord­ing to the re­port, which con­sisted of an over­view of past stud­ies.

Re­search al­so should ex­plore what might cause ALS among vet­er­ans, the au­thors said; one pos­si­ble rea­son is simp­ly in­tense phys­i­cal ac­tiv­i­ty. A study pub­lished in the Jan. 5, 2005 is­sue of the re­search jour­nal Brain found what its au­thors called “severely in­creased risk” of the dis­ease among Ital­ian pro­fes­sion­al soc­cer play­ers, for in­stance. That was one of a num­ber of stud­ies in­ves­ti­gat­ing a link between the dis­ease and phys­i­cal act­i­vity, but some of these found no tie.

Oth­er pos­si­ble rea­sons for the hints of in­creased sus­cep­ti­bil­ty among vet­er­ans, ac­cord­ing to John­son and col­leagues, are chem­i­cals, cig­a­rette smok­ing, al­co­hol, or trau­ma.

There has been a lack of high-quality stud­ies link­ing mil­i­tary serv­ice to Lou Gehrig’s dis­ease, the au­thors said. The best stu­dy, they wrote, was one that in­clud­ed more than 500,000 non-vet­er­ans and vet­er­ans who served be­tween 1910 and 1982. It found that the vet­er­ans were 50 per­cent more like­ly to have died with a no­ta­tion of ALS on their death cer­tifi­cates than the oth­ers. The study ap­peared in the Ju­ly 12, 2005 is­sue of the re­search jour­nal Neu­rol­o­gy.

ALS is nicknamed after Lou Gehrig, a hall-of-fame baseball player for the New York Yankees who was diagnosed with ALS in the 1930s.

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A U.S. government report has found “limited and suggestive evidence” that military service increases the risk for the devastating, gradually paralyzing Lou Gehrig’s disease. But hard physical activity—rather than the service itself—might explain the link, the authors added, in light of some studies suggesting professional athletes are also at risk. The degenerative nerve disease, formally known as amyotrophic lateral sclerosis, or ALS, affects roughly 0.01 percent of the U.S. population. Victims suffer a progressive breakdown of nerve cells that control the muscles, eventually causing paralysis and usually death. The report was released Nov. 10 from the Institute of Medicine, a part of the U.S. National National Academy of Sciences. The evidence linking military service to the disease “is rather sparse, so we could not reach more definitive conclusions at this time,” said Richard T. Johnson, a neurologist at Johns Hopkins University in Baltimore, Md. and chairman of the committee that wrote the report. “Because ALS occurs so rarely, any individual veteran’s chances of developing the disease are still low.” More high-quality studies on the relationship between military service and ALS are needed, according to the report, which consisted of an overview of past studies. Research also should explore what might cause ALS among veterans, the authors said; one possible reason is simply intense physical activity. A study published in the Jan. 5, 2005 issue of the research journal Brain found what its authors called “severely increased risk” of the disease among Italian professional soccer players, for instance, one of a number of studies . Other possible reasons for the hints of increased susceptibility among veterans, according to Johnson and colleagues, are chemicals, cigarette smoking, alcohol, or trauma. There has been a lack of high-quality studies linking military service to Lou Gehrig’s disease, the authors said. The best study, they wrote, was one that included more than 500,000 non-veterans and veterans who served between 1910 and 1982. It found that the veterans were 50 percent more likely to have died with a notation of ALS on their death certificates than the others. The study appeared in the July 12, 2005 issue of the research journal Neurology.