Walking Is Very Good For You (Up To Three To Four Miles A Day)

The body text of the meta-analysis cited below explains in language more clear than the abstract that:

Compared with adults in the lowest steps per day quartile, adults in the highest steps per day quartile had a 40% to 53% lower risk of mortality. Taking more steps per day was associated with a progressively lower risk of all-cause mortality, up to a level that was similar by sex but varied by age. There was progressively lower risk of mortality among adults aged 60 years and older until about 6000–8000 steps per day and among adults younger than 60 years until about 8000–10 000 steps per day. We found inconsistent evidence that step intensity was associated with risk of mortality beyond total volume of steps.

 

There are about 2500 steps per mile. So, for people under age sixty about three to four miles a day of walking is the most healthy (over age sixty three miles is the peak), and it doesn't matter much how fast one walks at a statistically significant level. 

At that level of walking the risk of death for a person under age sixty would be reduced by an impressive 47% compared to the risk of death for the lowest quartile of walking rates of significantly less than two miles a day. Significant health benefits, however, are available for most people from walking more, and especially for people who walk less than two miles a day.

Best fit values show that more than that much walking slightly increases your risk of death if you are under age 60, and is slightly health enhancing if you are over age 60. But, beyond the peak amounts of walking, the benefits or detriments aren't statistically significant, even in this very large sample of 47,471 adults pooled from 15 recent studies from Europe (4), Japan (1), Australia (1), the U.S. (8), and a study with data from 40 different countries.

The caveat, as always, is that correlation is not causation, even though statistically significant correlations in large samples generally have some cause. It could be that people who walk less do so because they suffer from a condition that simultaneously makes it harder to walk and increases their risk of death. 

The paper is:

Amanda E. Paluch, et al., "Daily steps and all-cause mortality: a meta-analysis of 15 international cohorts" The Lancet (March 1, 2022) (open access) DOI:https://doi.org/10.1016/S2468-2667(21)00302-9