Altitude and child development: A cross-sectional comparative study of children in urbanized low-altitude and rural high-altitude settings in Kyrgyzstan.

Childhood malnutrition remains a global challenge; Kyrgyzstan has reduced it, though disparities persist. We hypothesized that developmental differences between lowland and highland children reflect altitude adaptation, not malnutrition alone, obscuring monitoring. This study compared children from Naryn (2400 m) to Bishkek (800 m), examining respiratory, hematological, and anthropometric development. We conducted a cross-sectional study among healthy Kyrgyz schoolchildren aged 10-12 from Naryn and Bishkek. Measurements included anthropometrics, spirometry, hemoglobin, hand-grip strength, and vital signs. Linear regression controlled for socioeconomic, maternal, nutritional, and healthcare factors. Compared to Naryn (n = 143), Bishkek children (n = 123) were taller (2.7 cm, p = 0.006), heavier (2.7 kg, p = 0.008), with larger waist (2.7 cm, p = 0.007) and mid-upper arm circumferences (0.7 cm, p = 0.023), lower hemoglobin (-14.4 g/L, p < 0.001), higher oxygen saturation (2.1%, p < 0.001), weaker hand-grip strength (-1.3 kgf, p = 0.013), and higher HAZ (0.5, p < 0.001). No differences existed in BMI or BAZ. Naryn males were shorter than females (-3.60 cm, p = 0.024). Bishkek children had lower FEV1 (-0.4, p = 0.006) and FVC z-scores (-0.48, p = 0.003). High-altitude Kyrgyz children showed developmental and respiratory patterns suggesting physiological adaptation, though malnutrition cannot be excluded. Lower birthweight partially explained reduced height but not lung function or male-specific growth, highlighting the need for altitude-specific growth and respiratory references and continued research in pediatric high-altitude populations.