ALS increasing, what can clustered data tell us?

I found this 2005 report, Amyotrophic Lateral SclerosisA report on the state of research into the cause, cure, and prevention of ALS, and what jumps off the pages for me are:

• ALS is increasing in western societies, in particular in women and in younger age brackets.
• There have been a couple places identified where the incidence of ALS is 50 to 100 times the norm, which is Guam and the Kii peninsula in Japan.  In Guam there has been a steady decline in the rate of ALS making researchers believe that is may be related to traditional practices.
• There are incidents of married couples both getting ALS, which is highly improbable.
• Increases were most dramatic in Canada and the US, especially between 1979 and 1997, and follow-up show it was still increasing in the year 2000.
• A small number of studies show detectable evidence of viruses in the spinal cord of some ALS patients.

So this cluster data really interests me.  So, I did a bit of a search on Guam and I found this book, Science of Pacific Island People: Fauna, Flora, Food and Medicine.  

And then I look at the Kii Penisula in Japan and do a search and I find this article "False sago palm harbours deadly amino acid."  And, what do I read in what I have access to in that report???

Although this cycad is found all over the Western Pacific, from Japan to Australia, people eat its fruit only in certain areas, including the islands of Guam and Rota. The plant is also used in traditional medicine in the Kii Peninsula of Japan, and the Jaya region of New Guinea. It is mainly in these regions that a devastating neurological disease, known as Guam disease, is found. It resembles Parkinson's and Alzheimer's diseases, as well as a disease called amyotrophic lateral sclerosis. The brain and spinal cord degenerate, leading to dementia, paralysis and death.

And another report on ALS in the Kii Penisula says it was decreasing in the 60s and 70s and then started to increase again in the 90s in Hohara, shown in this map.

Another report dismisses a "cycad" as the cause.

There are a ton of other herbs used for traditional medicines and that knowledge of traditional medicines as been declining, but there also seems to be a push to bring it back.

One of the things the 2005 report says that I concur with is that some people are saying the disease is increasing because people are living longer, but if people are getting at a younger age, then this living longer has nothing to do with it.

Another thing, if mitochondria are showing problems well ahead of people noticing any symptoms, there could be a disconnect with people thinking something more recent being involved in the onset of their disease.

Now, married couples, that could be common exposure, food or microbe.

The viruses in the spinal cord could be related to leaky gut, and I found this about it.  

The barrier function becomes compromised, so that bacteria, viruses, undigested food particles and toxic waste products can leak from the inside of your intestines through the damaged digestive lining into your bloodstream, where they're transported throughout your body and can trigger your immune system to react. The end result is inflammation in various parts of your body, leading to a wide variety of symptoms like bloating, cramps, fatigue, food sensitivities, flushing, achy joints, headache and rashes.

When the 2005 report says:

In the absence of a clear understanding of the genetic or viral origin of sporadic ALS Epidemiology of ALS   (or the possible interaction of genetic susceptibility, viral infection, and exogenous factors in bringing about the disease),

I think they are dead on suggesting it is a combination of genetics, viral infection and then something else setting it off.