There was a piece in the New Scientist a couple of years ago that said type 1 diabetes seems to be correlated with higher latitudes. They suggested it was related to Vitamin D.
Yes, like MS, type 1 diabetes is considered to be an autoimmune disease. It's surprising to me as someone who hasn't studied medicine how related to each other autoimmune issues seem to be. Rheumatoid arthritis and latitude is another one that follows this same pattern. This article from 2010 about rheumatoid arthritis also mentions the link to low vitamin D levels, and that the link isn't understood.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2920915/