Age of pubertal events among school girls in Lagos, Nigeria

Background: Globally, there is a secular trend towards the reduced age for sexual maturity and menarche. This study aimed to determine the current age and factors associated with attainment of various stages of puberty in Nigerian girls. Methods: This study was a cross-sectional study involving 800 girls aged 6-15 years. The subjects were selected by stratified random sampling method from schools in Oshodi Local Government Area, Lagos State. They were interviewed and a physical examination was carried out to classify them into the various Tanner stages of breast and pubic hair maturational stages. Results: The median age of girls at first stage of breast maturation (B2), first stage of pubic hair development (PH2) and at menarche were 9.0, 9.0 and 12.0 years, respectively. Breast development was significantly related to normal nutritional status (adjusted odds ratio [AOR] 4.5, p < 0.001), overweight (AOR 40.2, p < 0.001), obesity (AOR 154.2, p < 0.001) and upper social class (AOR 15.7, p < 0.031). Pubic hair development was significantly related only to overweight (AOR 4.7, p < 0.007) and obesity (AOR 15.7, p < 0.001) while achievement of menarche was significantly related to overweight (AOR 0.1, p = 0.005), obesity (AOR 0.1, p = 0.0009), high social class (AOR 4.7, p < 0.001) and being a member of the Hausa tribe (AOR 35.8, p < 0.029). Conclusions: There is decline in age of pubertal maturation of girls in Nigeria and the major contributory factors appear to be overweight and obesity. These findings are consistent with the pattern in developed countries.