my mom has a history of breast cancer in her family and every once in a while I worry about that. my dad has been a heavy smoker his whole life so there's always that fear of heart attacks or throat cancer. I try not to think about it.
this kind of reminds me though, a few days ago someone my dad knows, who was a similar age to him, had a sudden heart attack and died and we're still not really sure why, but my dad was FREAKING out about it, he called me up and he was crying and the idea of "what if it had been him" scared him so much that he wanted to see me and my brother right away...
unfortunately health problems with older people is just a thing of life that I think very few people can fully escape. I hope your dad is okay.