The author's themselves acknowledged this very point as the most important weakness of the study:
Firstly and perhaps most importantly, selection
bias is possible because individuals who are at higher
risk of developing Alzheimer’s disease may be less
likely to enter or remain in memory intensive driving
occupations such as taxi and ambulance driving.
This could mean that the lower Alzheimer’s disease
mortality observed in these occupations is not due to
the protective effect of the job itself but rather because
those prone to the disease may have self-selected out
of such roles. However, Alzheimer’s disease symptoms
typically develop after patients’ working years, with
only 5-10% of cases occurring in people younger than
65 years (early onset).
Their explanation however only holds if pretty much all taxi drivers retire at 65 which is clearly not the case. It also ignores the relative prestige of professions. If your father both owned a store and drove a taxi for awhile which will you put on the death cert? Then do airline pilot plus owned a store.
Also dunking on studies is very much the point. The goal is to challenge beliefs and figure out where we are wrong.
We're well short of an obvious slam dunk. We're into a caveat that applies 5-10%% of the time, presented (perhaps disingenuously) as a personal "aha" in a curt, unjustified, and completely dismissive manner on a post that didn't deserve it. Just bad discussion all around, so I stick by the pushback. But it no longer matters - better discussion was had by all in other threads.
Firstly and perhaps most importantly, selection bias is possible because individuals who are at higher risk of developing Alzheimer’s disease may be less likely to enter or remain in memory intensive driving occupations such as taxi and ambulance driving. This could mean that the lower Alzheimer’s disease mortality observed in these occupations is not due to the protective effect of the job itself but rather because those prone to the disease may have self-selected out of such roles. However, Alzheimer’s disease symptoms typically develop after patients’ working years, with only 5-10% of cases occurring in people younger than 65 years (early onset).
Their explanation however only holds if pretty much all taxi drivers retire at 65 which is clearly not the case. It also ignores the relative prestige of professions. If your father both owned a store and drove a taxi for awhile which will you put on the death cert? Then do airline pilot plus owned a store.
Also dunking on studies is very much the point. The goal is to challenge beliefs and figure out where we are wrong.