| dc.description.abstract | Aim: Chronic mountain sickness (CMS) is more common among Han Chinese immigrants who have immigrated from inland China (from low altitude to high altitude Tibet) than among native Tibetans living at the same altitude. The prevalence of CMS is higher in inhabitants who live at a higher altitude compared to those who live at lower altitude in Tibet. However, there is still no definite answer to the question why CMS occurs. Early detection of risk factors in CMS is solicitously needed. Therefore, the aim of the present study is to give descriptive data and to investigate possible differences between native Tibetan and Han Chinese children living in Lhasa at 3700 meters above sea level and native Tibetan children living in Tingri at 4300 meters above sea level, with respect to selected factors, which may increase the risk of development of CMS, such as lung function, hemoglobin concentration, and arterial oxygen saturation.
Methods: Two cross sectional studies were conducted among 9-10 year old Tibetan (n=406) and Chinese (n=406) children living at 3700 meters (Lhasa) in 2005, and the same age for Tibetan children (n=444) living at 4300 meters (Tingri) in 2007. A total of 1256 (667 boys and 589 girls) children participated. Lung function including Forced expiratory volume in 1 seconds (FEV1), Forced vital capacity (FVC) and Forced expiratory flow 50% (FEF50), hemoglobin concentration, and arterial oxygen saturation at rest were measured using standard methods. Heart rate and anthropometric measurements were also recorded. Questions about demographic characteristic, parental smoking, diet, socioeconomic factors and physical activity were provided from a questionnaire.
Results: After adjusting lung function values for sex, age, weight, height and duration of living in Tibet, Tingri Tibetan children had statistically significant higher FEV1 and FVC values than Lhasa Tibetan children who had significantly higher values than Lhasa Chinese children (Tingri Tibetan vs. Lhasa Tibetan vs. Lhasa Chinese: FEV1: 1.86 (1.83-1.88)L vs.1.76 (1.74-1.78)L vs.1.66 (1.63-1.68) L; FVC: 2.13 (2.10-2.16)L vs.1.97 (1.94-1.99)L vs.1.88 (1.85-1.91) L). Both native Tingri Tibetan and Lhasa Tibetan children had significantly higher FEF50 than Han Chinese children (Tingri Tibetan vs. Lhasa Tibetan vs. Lhasa Chinese: 2.76 (2.67-2.85)L/s vs. 2.72 (2.64-2.79)L/s vs. 2.35 (2.27-2.44) L/s). The difference was not statistically significant between Tingri and Lhasa Tibetan children for FEF50.
Tingri Tibetan children had statistically significant lower hemoglobin concentration compared to Lhasa Tibetan children who had significantly lower hemoglobin concentration than Lhasa Han Chinese children (Tingri Tibetan vs. Lhasa Tibetan vs. Lhasa Chinese: 14.0 (13.9-14.1) g/dl vs.14.6 (14.5-14.7) g/dl vs.15.3 (15.2-15.5) g/dl).
There were no differences between Tingri Tibetan, Lhasa Tibetan and Lhasa Chinese in heart rate at rest. Tingri Tibetan children had significantly lower arterial oxygen saturation than both Lhasa Tibetan (Tingri Tibetan vs. Lhasa Tibetan: 87.2 (86.7-87.8) % vs. 91.1 (90.8-91.3) %, p<0.001) and Lhasa Han Chinese children (Tingri Tibetan vs. Lhasa Han Chinese: 87.2 (86.7-87.8) % vs. 90.4 (90.1-90.7) %, p<0.001). Lhasa Tibetan girls had higher arterial oxygen saturation than Lhasa Han Chinese girls (girls: 91.1 (90.7-91.5) % vs. 90.2 (89.6-90.7) %, p<0.05). But for boys there was no difference.
Conclusion: Tingri Tibetan children (4300m) had better lung function values FEV1, FVC and FEF50 and lower crude haemoglobin concentration than Lhasa children (3700m). The FEF50 difference between Tingri Tibetan and Lhasa Tibetan children was, however, not statistically significant. If poor lung function is associated with increased risk of CMS at old age, the results may indicate that Tingri Tibetan children have lower risk of CMS than Lhasa children. At the same altitude (3700 m), Lhasa Chinese children had lower lung function values FEV1, FVC and FEF50, and higher crude haemoglobin concentration than Lhasa Tibetan, also seems that Lhasa Han Chinese will have a higher risk of later development CMS. A prospective study, following the children to the age when CMS occurs would give answers to this hypothesis. However, it is more likely that other factors modify the risk during the years up to adulthood, resulting in higher risk of CMS with increasing altitude. Regarding haemoglobin concentration and arterial oxygen saturation, more analyses on adjusted values need to be done in order to conclude the possible differences between groups. | eng |