[oh_sigh]

Vertigo seems possible, especially since altitude induced vertigo is a thing, and Mexico city sits at 7300' above sea level. That's usually not enough to affect a healthy middle-aged-or-less person, but an obese 70+ year old? Definitely possible.

Unfortunately, altitude can also trigger strokes, at least through polycythaemia.

A key question for internet sleuths would be - did he just show up in the city, or has he been there for a while? Polycythaemia takes time to develop so he would need to be there for at least a few weeks before it could play a role in inducing a stroke.

[channel_t]

I was about to say, I've brought friends from the US to Mexico City on a few occasions and it seems like the altitude (and maybe the pollution) has had strange and unpleasant effects on most people during the first couple days. A vertigo episode definitely doesn't sound far-fetched.

[capableweb]

I've found out that chewing coca leafs is an excellent way to combat side-effects from changing altitudes. Mostly socially acceptable in central/south america as well, so don't have to worry about that. Doesn't hurt that you could replace your coffee-intake with it as well :)

[0xDEADFED5]

or we can just not be creepy and leave him alone?

[oh_sigh]

A good point. We must avoid creepiness at all costs, DEAD FEDS.