I would be interested to see the statistical studies behind the reasoning. When was the last time it was studied?I'm just one data point, but I suffered from asthma from about 8-11 years old - probably due to growing up in a damp house without central-heating in northern england then going to an even colder and damper boarding school. So the RN turned me down for aircrew, despite having been in the UAS, winning a blue for modern pentathlon at Cambridge, getting a first class aero engineering degree, and being the only candidate ever to succeed in doing a supposedly impossible shark-infested custard test at the AIB. Anyway, I went on to pass SAS selection instead, can still (aged 45 now) row 2000m in 6:45, did the 52nd fastest C2 marathon rowing time worldwide last year, needless to say have never had a stroke of asthma since, and now hold ATPL.