Taken from the actual study:

https://www.ijidonline.com/article/S1201-9712(20)30534-8/ful...

* Overall in-hospital mortality was 18.1% (95% CI:16.6%-19.7%);

by treatment:

* hydroxychloroquine + azithromycin, 157/783 (20.1% [95% CI: 17.3%-23.0%]),

* hydroxychloroquine alone, 162/1202 (13.5% [95% CI: 11.6%-15.5%]),

* azithromycin alone, 33/147 (22.4% [95% CI: 16.0%-30.1%]),

* and neither drug, 108/409 (26.4% [95% CI: 22.2%-31.0%]) .

And the conclusion:

> In this multi-hospital assessment, when controlling for COVID-19 risk factors, treatment with hydroxychloroquine alone and in combination with azithromycin was associated with reduction in COVID-19 associated mortality. Prospective trials are needed to examine this impact.

Right. Their confidence intervals overlap: 17.3%-23.0% vs 22.2%-31.0% Factor in multiple hypothesis testing and it's worse than presented.

I couldn’t figure out from the paper what was the criteria for giving each of the drugs.

Seems it was not random which is a minus, but

>The combination of hydroxychloroquine + azithromycin was reserved for selected patients with severe COVID-19 and with minimal cardiac risk factors.

This group still saw improvement over no treatment, which is a huge plus(unless cardiac function is correlated with covid susceptibility).

> unless cardiac function is correlated with covid susceptibility

Chronic heart disease is a factor associated with higher risk of COVID-19-related hospital death, https://www.medrxiv.org/content/10.1101/2020.05.06.20092999v... gives a hazard ratio of 1.27 adjusted for all the many other factors they looked at.

So yes, it looks to me like at least some of what this Ford study measured was indeed that difference between people with pre-existing conditions dying at a higher rate than people without.