isn't this just an observational study? it doesn't "prove" anything.
it doesn't account for WHY some don't consistently take the drugs, and most importantly is not randomized.
the groups may be self selected, if not much is happening down south, i bet people are less likely to use the drugs
i can only speak for myself but i am in the group that doesn't consistently use PDE's. that's because they didn't seem to make a difference and i admit, some apathy on my part. but it has been shown that your sex post op is proportional to how your sex was preop.
here's a study taking about
other factors fwiw
www.ncbi.nlm.nih.gov/pubmed/22520165dave
dave