1. High Incidence from the 1940s through 1960s
Guamanian ALS is a rare form of ALS that had a high incidence in the US territory of Guam from the 1940s through 1960s. The rate of ALS in this area increased by 50 to 100 times its previous incidence during these years, causing serious concern among health officials and killing 10% of Guam's native Chamorro people. Areas of Japan, New Guinea and Indonesia were also affected. The incidence of Guamanian ALS has dropped since the 1960s and is now rare in those born after this time.
2. Associated with Parkinson's and Alzheimer's Disease
Unique among the Guamanian form of ALS is its association in many instances with symptoms of Parkinson's and Alzheimer's disease. Other forms of ALS usually do not affect the brain or mental function, instead damaging only nerves that control muscle function. Those with Guamanian ALS however, showed the loss of muscle and motor function typical of ALS, but they also had a loss of cognitive function similar to Alzheimer's disease plus the tremors associated with Parkinson's disease.
3. Food Toxins
It is now believed that dietary factors may have been the cause of Guamanian ALS. People in these areas were consuming flours made from a specific type of tropical plant called a cycad, which resembles (but is unrelated to) palm trees. The nuts and seeds of these plants contain a toxin that damages the nervous system. Scientists have discovered that native people of Guam were also eating bat meat around this time period. The bats in this area fed on large amounts of cycad fruits, which led to increased levels of the neurotoxins in their blood and flesh. These toxins could have been passed on to people who ate the bats as food. The incidence of Guamanian ALS dropped as people stopped eating bat meat.
4. Unfiltered Drinking Water
Guamanian ALS may also have been due to toxins found in unfiltered drinking water. Some scientists believe that algae and bacteria in the rivers of Guam and other affected countries produce high levels of nervous system toxins during certain times of the year. During the time frame prior to the late 1960s the drinking water in these areas was not filtered. People may have consumed high levels of these toxins, leading to the brain and nervous system damage associated with Guamanian ALS.
5. Genetic Predisposition
Native populations of Guam have very recently been found to carry genetic mutations that may make them more susceptible to Guamanian ALS. Studies of Chamorro families show that specific genes may be affected and may increase the risk of developing this form of ALS. While there is not yet a genetic test for Guamanian ALS, you should see your doctor for a comprehensive evaluation if you have a family history of ALS, experience chronic or progressive muscle weakness, have difficulty swallowing or breathing, or are concerned that you may be at risk for this or other forms of ALS.
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