The overall dataset was very large (8,972,221 deaths), but only 1,348 ambulance drivers were included, and just 10 had Alzheimer’s disease as the underlying cause of death.

Such a small number of outcomes matter because statistical precision depends on the number of relevant events. With only 10 Alzheimer’s deaths, even a small change in the count could substantially alter the estimated association.

Taxi drivers provided more robust data, with 171 Alzheimer’s deaths among 16,658 decedents, but death-certificate Alzheimer’s mortality may not reflect how often taxi drivers develop the disease. Differences in diagnosis or cause-of-death reporting across occupations could influence the observed association.

The large overall sample does not eliminate uncertainty in the much smaller occupational subgroups, particularly among ambulance drivers.

Nonetheless, this is an interesting study and merits further investigation.