title: Cross-sectional study of congenital heart disease among Tibetan children aged from 4 to 18 years at different altitudes in Qinghai Province.
abstract: BACKGROUND
  Congenital heart disease (CHD) is a common heart condition which does considerable harm to the health of children and adolescents. CHD epidemiological characteristics of Tibetan children whose ages ranged from 4 to 18 years were investigated in Qinghai Province.
  
  
  METHODS
  A total of 32 578 Tibetan children, living at altitudes of 2535 m, 3600 m and 4200 m, were examined using a three-stage protocol: prescreening, rechecking and diagnosis using a color Doppler. The distribution of CHD at different altitudes was analyzed together with differences in occurrence according to age and gender.
  
  
  RESULTS
  A total of 235 CHD cases were discovered. The total prevalence of CHD was 7.21 per thousand. Prevalence of CHD has been shown to increase along with increase in altitude with 5.45 per thousand at an altitude of 2535 m, 6.80 per thousand at 3600 m and 9.79 per thousand at 4200 m. There were no statistically significant differences between the prevalence at 2535 m and 3600 m (chi(2) = 1.594, P > 0.05). However, there was a significant difference between the prevalence at 2535 m and 4200 m (chi(2) = 7.002, P < 0.01). Also, apparent differences existed between the prevalence at 3600 m and at 4200 m (chi(2) = 5.540, P < 0.05). There was no statistically significant difference in prevalence according to age at an altitude of 2535 m, but the rate of CHD increased significantly along with increasing age at 3600 m and 4200 m. The total prevalence ratio of children aged from 16 to 18 years was significantly higher than that of children from 4 to 7, and from 8 to 12 with chi(2) values of 10.79 (P < 0.005), and 5.60 (P < 0.05) respectively. Within the constituent ratio of CHD, the prevalence of atrial septal defect (ASD) was the highest at 39.10%, followed by the prevalence of ventricular septal defect (VSD) at 32.8% and patent ductus arteriosus (PDA) at 24.7%. Furthermore the proportion of the four categories of CHD varied at different altitude levels: at 2535 m, of those diagnosed with CHD, the prevalence rate of VSD was the highest at 43.5%, at 3600 m ASD was the highest at 42.8% and at 4200 m, PDA was the highest at 50.8%.
  
  
  CONCLUSIONS
  The epidemiological characteristics of CHD in Tibetan children may be associated with altitude levels.
authors.affiliation: Central Laboratory, Qinghai Cardiovascular Diseases Vocational Hospital, Xining, Qinghai, China. chqh666@yahoo.com.cn
authors.forename: Qiu-hong
authors.initials: QH
authors.lastname: Chen
authors.forename: Xiao-qin
authors.initials: XQ
authors.lastname: Wang
authors.forename: Sheng-gui
authors.initials: SG
authors.lastname: Qi
mesh_terms: D000293:Adolescent; D000531:Altitude; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D003430:Cross-Sectional Studies; D005260:Female; D006330:Heart Defects, Congenital / Q000453:epidemiology*; D006801:Humans; D008297:Male; D018609:Tibet / Q000453:epidemiology