The easy answer is no. There are theories relating to exposures or activity or sleep cycles or immunizations/vaccines but as it stands right now none are proven. The Registry which the VA ran may shed some light but to my knowledge nothing has been released.
There is a particularly higher rate of ALS among Gulf War vets of 1990-1991 which has caused the VA to get involved. I'm one of those vets (did 20 yrs in the navy) and have developed symptoms that mirror ALS. So far, the neuros haven't been able to make any kind of difinitive diagnosis. Theres the weakness, hyperreflexia, stiffness, twitching and some atrophy in my right arm that may or may not be attributable to the rest of whats going on. Anyway, in the military, your sleep pattern is constatly being disturbed and stress levels can go through the roof. Oh, not to mention diet! The food isn't exactly lean cousine kind of stuff. But, I'd do it all over again in a heart beat (which I may not have a whole lot left - lol).
The studies show that the risk of developing ALS are higher for all veterans regardless of time or place of service not just those who served in GW1. That study actually showed a 40% greater risk for naval personnel than the ones done on GW vets only. That and the IOM review supporting the Weisskopf study are the basis for H.R. 5454 and the rumored regulatory changes to be made by Secretary Peake.
I am asking everywhere but guess there is no general amount of letters needed. I have 2 so far by can get one from Johns Hopkins also so hope that satisfies them. I am very irritable now because of this and have to catch myself constantly That is why I am afraid to deal with the VA as I know I will be very short with them. Not on purpose it just blurts out. At home I am not so bad and never raise my voice to my wife.
I have so many doctors involved but I do not use the VA Hosp except the local clinic for my minor aids and things like BP medication and general physical stuff. My Primary care doctor who used to be my VA Primary care Doctor till he left is the one who gave me an official diagnoses letter for the VA, as if they VA had to go through all the records it would take a year. The stack is now about 2 ft high. He just said it should go much quicker and faster if he put it all in one condensed letter with all the test that were done and everything that was ruled out. Prior to that the previous records are just reems of papers with every possible guess you could think of. I cannot think of any test that was not done or illness that was not rulled out prior to them finaly saying it was ALS. Now the VA did request a release to be signed for all the Doctors and Johns Hopkins but I do not think they have any idea of the amount of paperwork they are talking about. No one at the VA is going to read all that material and the cost to the Doctors to make copies of it all is going to be redicilious. But I signed the releases and guess they will fight it out on who will copy what. The VA Hosp here is in Wilmington about 1.5 hr away and while they are not really a bad hosp I do not think I would changed from Hopkins but again that said Hopkins has made some real blunders also, so none of them are perfect. My primary Care Doc is amazing how he keeps up with it all and cordinates everything for me. That is why when the VA dropped his clinic and opened their own I stayed with him.