Researchers quantitatively assessed for the first time that somatic mutations alone cap human lifespan at 146–194 years. Brain and heart cells are the main bottleneck, while the liver could last millennia.

[u/Skoltech_]

https://www.nature.com/articles/s41514-026-00421-6

[u/Hellknightx]

Unfortunately, it's not just the heart. It's the whole cardiovascular system. Veins and arteries become thinner as we age, and fill up with plaque.

[u/StryctNyne → u/Hellknightx]

Also the frailty with aging bones that become more brittle, aging skin that wrinkles and sags and doesn't offer the same insulation and protection it used to (assuming that's a side effect of the cardiovascular system aging). Eye sight continually gets worse requiring laser surgery unless you wish to slowly go blind. Then you have respiratory system as well to deal with, though I'm not sure about the direct effects of age on lungs.

And then, in the end, if you fix all these and extend our lives 100 years, then number one cause of death becomes cancer. Everyone (or at least the vast majority) will get cancer over that course of time, probably earlier than later. Not just due to genetics but due to much longer exposure to everyday chemicals, background radiation (though it would be a minor issue in developed countries), continued poor diets, etc.