Ageing.
Anyways, most of the regions where demographics are shifting to a larger proportion of older persons also have much lower birthrates.
See e.g. https://leapsmag.com/anti-aging-pioneer-aubrey-de-grey-peopl...
I think he'd say living longer for remaining disease-free would just be a happy side-effect.
That said, there many companies working on aging biology now: http://agingbiotech.info/companies/