Do people who work in aviation (pilots and flight attendants) usually develop haemolytic anaemia? and if yes, why?

Flying not a risk: Hemolytic anemia is due to the breakdown of red blood cells. It does not appear to be more common in those working at high altitude. It has hereditary causes from red blood cell & hemoglobin defects, and extrinsic causes including auto-immune disease and drug effects. There are anemias associated with being at high altitude, but pressurized cabins help prevent these in aviation workers.

NO: In my many years as a Civilian & Military Flight Instructor and thousands of hour of flight time, I have never heard of any pilot developing this problem.