Are cpaps that widely used to have that significant of an effect?

For CPAP to be primarily responsible, we would need a very sizeable portion of the population to be using them, but I think the numbers are less than 3% right?

From the article as to the effect size:

“For example, in the US, among people aged 81 to 85, 25.1% of those born between 1890–1913 had dementia, compared to 15.5% of those born between 1939–1943,”

I'm not saying that CPAPs don't contribute, but they are not likely the main contributors.