My guess is they're genetically similar to other airline pilots. Pan Am's BK process put their pilots medical records into the public eye because the company provided the physicals in house. BK? The records became available. The records were used to look at life expectancy, longevity, etc. Same stuff despite the long haul/night flying operations they did - they lived longer than the average person. Researchers loved it because they had medical records of a select group (pilots) going back decades.