I make a point of assuming any deaths I don't know the cause of were strokes. It can happen at any age, and it keeps me from speculating about something more lurid.
I usually assume heart attack, that's kind of the other biggie.
Biggie-er.
Stroke/heart attack is still one of the top 3 killers in the US, and most people look for alternative explanations first, which makes little sense to me.