Objective      To investigate the prevalence of high altitude polycythemia (HAPC) and its influencing factors in native long dwelling Tibetans in Lhasa and Ngari Prefecture.       Methods      The survey was carried out on 2 757 adult native Tibetans who dwelled in Lhasa area (at an altitude of 3 680~3 800 m) or Ngari Prefecture (at an altitude of 4 400~4 700 m). Questionnaire survey and laboratory blood testing were conducted

and the results were analyzed with SPSS 13.0 software.        Results      There were 72 HAPC patients found among the 2 757 subjects

with a prevalence of 2.6% in the cohort. Univariate analysis indicated that the prevalence of HAPC was significantly higher in the Ngari Prefecture than the Lhasa area (5.2% vs 1.9%

P0.05)

in the males than the females (3.4% vs 1.9%

P0.05)

and in the smokers than the non-smokers (4.7% vs 2.1%

P0.05). Among different occupations

the prevalence was the highest in herdsmen (9.2%) followed by the self-employed (7.3%). But

the prevalence was the lowest in those having the lowest family’s month-earning (2.1%). There were no significant differences in the prevalence among the alcohol consumptions

education levels and ages (P0.05). Logistic regression analysis found that altitude (P0.01)

sex (P0.01) and occupation (P0.01) were influencing factors for HAPC.       Conclusion      The prevalence of HAPC is quite low for the native Tibetans dwelling in Lhasa and Ngari Prefecture. Altitude

sex and occupation are influencing factors for its occurrence.