army epidemiology
1.SETTING: the 71687 Force of Chinese PLA, the 71521 Force of Chinese PLA, Department of Epidemiology, Fourth Military Medical University of Chinese PLAPARTICIPANTS: By chester sampling, 122 aircrew and 122 ground crew of one army airmen in one stationed training troop were randomized in February 2001. The pairs were made at ratio of 1:1 according to age difference less than 3 years and same sex and nationality.
