Hematologic and spirometric characteristics of Tajik and Kyrgyz highlanders in the Pamir Mountains

Objectives In this study, we measured the hematologic and spirometric parameters of native Tajik and Kyrgyz highlanders in the Pamir Mountains to investigate adaptations to high altitude stressors. Methods Hematological parameters including arterial oxygen saturation (SaO2), red blood cell (RBC) counts, and hemoglobin (Hb) concentration were measured on Sarikoli Tajik (n = 80; 3100 m), Wakhi Tajik (n = 48; 3500 m), and Kyrgyz (n = 64; 3250 m) in comparison to lowland Uyghurs (n = 50; 1300 m). Spirometric parameters including forced vital capacity (FVC), the first second of forced expiration (FEV1), and forced expiratory flow between 25% and 75% (FEF25‐75) were measured. We also reported mountain sickness symptoms in these highlanders and conducted a multivariate regression analysis to analyze the association between these symptoms and the measured parameters. Results SaO2 of Sarikoli Tajik, Wakhi Tajik, and Kyrgyz (91%‐93.5%) are significantly lower than lowland Uyghurs, yet are comparable to other native highlanders at a similar altitude. RBC counts and Hb concentrations of all three highland populations are significantly increased compared to Uyghurs. FVC is lower in Sarikoli Tajik, Wakhi Tajik, and Kyrgyz (male: 3.48‐3.86 L, female: 2.47‐2.78 L) compared to Uyghurs. Combined with normal FEV1, elevated FEV1/FVC ratio, and FEF25‐75, the spirometric patterns of these highlanders indicate restrictive lung disease. A high prevalence of mountain sickness symptoms such as headache and nausea was found in all three highland populations, and are attributed to low FVC and aging by regression analysis. Conclusion Tajik and Kyrgyz highlanders showed adaptation in SaO2, RBC, and Hb level, but poor performance in spirometry, which causes mountain sickness.