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Observational studies are just observational studies. Most of them report spurious correlations. Their results cannot be taken at face value. Only through intervention studies you can demonstrate causation. Intervention studies (RCTs) --- the meta-analysis that I linked --- in this case report a null result (no effect) regarding hard end points (CVD and death).

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These intervention studies aren’t measuring what you’re suggesting they are measuring.

The specific question is if elderly people starting exercise late in life received similar levels of benefits. They then look at studies lasting between 1.4 and 5 years where the median participant age was between 72 and 78. The exercise group did have lower mortality but it wasn’t considered statistically significant.

Unless you’re 70+ and only planning on exercising for a few years they don’t say much about what you should be doing. Especially as by this age a significant percentage of the most sedentary people have already died.

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