It is just old age, with no regular exercise, and too much alcohol or smoking. I am much older than Biden, but I never smoked, gave up alcohol after age 50 and do regular exercise. I have zero medical issues.
Genetics also play a bug role in how well you age.
My father, paternal aunt, paternal grandfather and paternal great grandfathers all died in their 60s. My mother, maternal uncles, maternal grandfather and maternal great grandfathers all lived well into their 80s. I could go either way.