Flushing out 'zombie cells' could help stave off Parkinson's, study suggests

Senescent cells generate inflammation. So every age-related condition with an inflammatory component - which is most of them - should be improved to some degree by that factor alone when senescent cells are removed, even putting aside other effects of senescent cell accumulation.

Senescent cells are not the only source of inflammation - the immune system has other sources of dysregulation. The degree to which their contribution is important will vary tissue by tissue and condition by condition.

Some studies show that a large fraction of astrocytes are senescent in the old human brain. Much larger than is the case for senescent cell fractions by number in other tissues. Too large to just go in and clear them all out in short order - tumor lysis and outright failure of the brain would be on the menu. You'd have to clear them out slowly over a period of time, allowing for their replacement. It is probably good that first generation senolytics won't get past the blood-brain barrier, as they would be pretty hard to use safely otherwise.