If
The challenge is always parsing out the different variables. Common sense says that older, sicker individuals are more susceptible to just about every illness. And older folks tend to accumulate these chronic illnesses.
So are these variable really risk factors or is it just age...and old people tend to have these diseases.
Essentially, you need a multivariant analysis...which requires a significant sample size. I’ll read the studies when I get the chance and let you know what I think about the stats.