I'm being completely serious when I say (as a non-doctor), that unless they have a specific heart condition, I presume it would substantially lower if they did

I'm being completely serious when I say (as a non-doctor), that unless they have a specific heart condition, I presume it would substantially lower if they did some brisk walking. To give you another idea of just how low intensity "brisk" is, one indicator I've seen used is "you can talk in a conversation with relative comfort, but you couldn't sing without getting a bit out of breath". That's how general the advice is, and that's sufficient to improve longevity. More is better, but you're already somewhat close to the bottom of the J curve just doing that (marathon level and beyond is where more is worse again, if I'm remembering correctly). This isn't my original source, but what I found that seems to agree with my memory: 10.1016/j.pop.2013.08.002 There are recommendations for other exercise in there, but none of it is related to longevity, based on my skim.