I have't looked that deep into results of this particular study (hopefully peer reviews will do that: it would be unmanageable to look at everything) — but that

I have't looked that deep into results of this particular study (hopefully peer reviews will do that: it would be unmanageable to look at everything) — but that was not the GP's complaint, but rather that conditions of each region have not been taken into account, and I am saying that this is fine if numbers are sufficiently large and statistically relevant. You may be right that they are not, and hopefully that results in the paper being retracted.