Early deaths in young professionals

Not sure if this is a coincidence but lately I've seen quite a few working professionals in 30s die of heart attacks and other diseases. I don't get why a person that's in her early 30s dies of heart attack. They look fit and apparently none in their family had history of heart attacks. Is this because of increased stress and anxiety? I'm just hoping to find a common root cause so that many are aware of it and take good care of themselves before it is too late.