The local pilots lose their medicals just as often. When you fly for a Chinese airline you become part of their system.
Half way through my 2 year contract our "handler" sent us an email saying we were going to have to work hard because they were short of Captains. 39 out of 150 local Captains were Med down. The average age was probably 30-32.
Fat liver, sludgy gall bladder, nonexistent kidney stones, nonexistent brain tumors. Heart rate too low for those of us who run, Blood pressure too high when the the velcro is worn out on the BP cuff and they tell you to "hold it in place please".