Puberty in modernizing Kazakhstan: a comparison of rural and urban children.

BACKGROUND: Data on puberty development are available for several countries but not for Central Asia. AIM: Using data collected during the Kazakhstan Health and Nutrition Survey (KHA-ES), we evaluated the relationship between the living environment (rural vs. urban), ethnicity (Russians vs. Kazakhs) and pubertal status in children living in Kazakhstan. SUBJECTS AND METHODS: Genital (G1-G5), breast (B1-B5) and pubic hair (PH1-PH5) development were evaluated in a sample of 2389 boys and 2416 girls using Tanner's criteria. Age at menarche was evaluated using the 'status quo' and 'recall' methods. RESULTS: Rural children were older than urban children at stages > or =G2 for males and > or =B2 for females, and this difference was more evident for Russian males. Differences levelled out at later stages of development in Kazakh males and in the pooled girls. The living environment was slightly but significantly associated with median age at menarche (12.89 years for urban Kazakhs to 13.43 years for rural Kazakhs). Male and female Kazakhs were older than Russians at stages 4 and 5, especially in the urban area. CONCLUSION: A relationship between pubertal status and the living environment was present in a rapidly modernizing country such as Kazakhstan.