Timing of puberty in Iranian girls according to their living area: a national study

This study aimed to compare the timing of puberty between various geographic locations and different ethnicities. This national survey was conducted in 20 provinces in Iran. Healthy Iranian girls were selected from public schools using cluster random sampling. A total number of 30 clusters including 7493 girls, aged 6.0–20 years, were selected. In order to compare different areas, the national classification of the provinces based on climate, ethnicity, geographic locations, and socioeconomic variables were used. Accordingly, there are 11 regions in Iran. Analysis of variance was used to compare the mean ages of menarche, pubarche, and thelarche in different regions. Tehranian girls, with 11.99 ± 1.35 years (mean ± SD), had the lowest age of menarche which was statistically significantly. The second region with lowest age at menarche was Fars (12.40 ± 1.27 years). The mean age at breast bud stage (B2) was significantly lower in Ghazvin-Zanjan region (8.97 ± 1.45 years). In Fars region, the mean age at B2 stage of breast development (11.01 ± 1.88 years) was higher than other regions except for Mazendran-Guilan and Tehran-related cities. The mean age at public hair development at Tanner stage 2 (PH2) in Kordestan-Lorestan-Ilam region (10.70 ± 1.23 years) was significantly higher than other regions. We found significant differences in the age of pubertal stages of girls living in various regions with different ethnicity and geographic characteristics. Considering the impact of pubertal age on general health, more studies should be done about the lifestyle and environmental factors affecting the onset of puberty.