After suffering a severe concussion many years ago, I heard a friend tell my mom in the ER:
"He doesn't drink or smoke pot, and he killed all his brain cells anyway."
Apparently, this is how life is. If you're lonely, your health suffers worse than if you have severe health problems. If you don't have pets or children, you die earlier. If your life isn't a never-ending parade of hugs and love and mobs of social mobbery, you will not last long on this cold, cruel Earth.
Which leaves the prospect that you can work out, abstain from cigarettes and other vices and still kill yourself through lone-besity and antisocial smoking. Even if it's largely beyond your control and you're not so unhappy about it.
I understand as well as anyone the crippling effect of loneliness (which isn't necessarily a function of place or lack of support). It messes with your head in sometimes very subtle ways. You may feel the need to reach out to your fellow human, but you also trust strangers less. You may seek out those with whom you share interests, but not bond with them. You want a break from your personal routine, but you tolerate others' quirks less and less. Possibly worst of all, you do lash out more (whether alone or with others) than you might if you felt more like part of society. You get caught up more in your own thoughts and criticisms, which can be mentally destructive if there isn't anyone around to check them. If your circumstances don't easily allow for you to attend events or meet anyone, that can lead to a lingering depression. It's not a stretch to see how all that could lead to a shorter lifespan.
On the other hand, not everyone can easily obtain, or is cut out for, the kind of life that supposedly keeps people alive longer. Who's to say that handling a brood of children and creatures wouldn't drop me into the ground? To quote Ned Ryerson, "It's all just a big crapshoot anyhoo."
I know what's shortening my lifespan — reading about all the ways being yourself kills you.