It could be attractive people have had more romantic partners at some point (or are more social in general?) and that is how they got the condition in the first place. Could possibly attractiveness, instead of being an effect, be indirectly a cause through romantic activities or social activities? How many different romantic partners (from their estimation, solely kissing or further) they have ever had might especially relate rather than just amount of sex in general (which could be one partner). It could be those considered less attractive are more likely to either have less romantic activity and/or are more likely to "settle" on one romantic partner, and those who are considered more attractive have a longer period of trying out various partners at some point in their life because it is easier for them, leading them to be more likely to get this condition.