A specific gene has not been definitively associated with Dupuytren’s, but the best evidence suggests that the primary cause is genetic. There are factors which alter risk, such as diabetes

Treating Dupuytren’s with vitamin E. Does it work? No, according to this 50 year old study, documenting results with before and after plaster casts of the bent fingers. The results:

In the Viking era, boats from what is now Denmark travelled west across the North Sea to invade what is now Great Britain, but boats from what is now Sweden