Lefthanded, I don't see the map of MS prevalence.

Dr. Swank and many others have documented that MS occurs more frequently in northern climates. What is the reason? Could be the Vitamin D theory. Also, MS occurs more frequently in the "native" populations of Scandinavia and the British Isles than among the Mediterraneans, but this has probably changed by now, since people move around much more than they used to, so it may not be a racially inherited disorder. I have several people in my family dx'd with MS, always the ones in the Pacific Northwest of America, but the matter is blurred in my case, since I am not sure if our ailment was/is MS plus Porphyria, Porphyria solo, or MS solo--all of these possibilities suggested by doctors over the years. My grandma had "it", and her sister's nine children seem to have produced only one known MS diagnosis, but I did not know the whole family well. The families were estranged over religion, which is a most unfortunate thing. I would know my cousins and second and third cousins if it were not for this. The one dx in my grandma's sister's children was in a man who died young by drowning, soon after his MS dx, so who knows if he would have had a more complex dx if he had grown older. I almost died of drowning when I was near his age, but was rescued...I became paralyzed in the heat while swimming in a deceptively deep creek.
Now I have to avoid sun like the plague, due to Porphyria, which is hard in my sunny climate, but I cover head to toe with Solumbra cloth clothing. I take Vitamin D3.