People with excess brain capacity are able to easily acquire spatial reasoning, and can (more) easily work/qualify for ambo and taxi jobs. Their excess brain capacity makes progressive brain damage more difficult to impact them before other causes of death.

- Drivers with early symptoms of Alzheimer’s struggled to remain effective and changed profession

I'm sure that the study accounted for this, but some fun ones

1. Ambo and Taxi drivers are vastly more likely than the general population to die in a collision before Alzheimers gets to them. 2. Even if you control out collisions, driving an Ambo and Taxi requires enough more memory and cognitive functioning to survive that people with early Alzheimer symptoms are significantly more likely to die in a collision, meaning you've controlled out a good chunk of ALzheimer victims in the process.

Pure speculation here. Driving is a sedentary occupation which might increase the percentage of deaths attributable to a sedentary lifestyle, with consequent decrease for Alzheimers?

Ambulance drivers were close to medical professionals and got good, early diagnosis and care.

Taxi drivers were exposed to a wide variety of people who they conversed with, became aware of Alzheimer's symptoms and treatments and sought help early.

Off the top of my head.

It's about hippocampal size, so people with a larger hippocampus are less likely to get alzheimers as it's a barrier, lots of studies scanning London cabbies brains and they have enlarged hippocampus - it's believed to give a barrier against alzheimers.

So spatial navigational ability is another risk factor/biomarker (along with blood pressure, smoking etc)

Social interaction while spatially reasoning also helps. (Social + cognitive load)

I haven't read the article, but what if:

The problems arrizing from alzheimers are so problematic, that the cabdrivers / ambulance drivers drive themselves to death before they enter the stats as alzheimers patients?

A bit like the famous bullet holes in planes from ww2