Age at menarche in Nigerian demographic surveys

Age at menarche was investigated using data collected from demographic surveys (WFS, DHS) conductedin Nigeria between 1982 and 2018, all of which were based on large representative samples of the femalepopulation. Linear-logistic regressions were used to estimate mean age at menarche, its trends and its riskfactors. Mean age at menarche had underwent a marked secular decline from 15.02 years for girls born in 1933 to 13.78 years for girls born in 2003. In multivariate analysis, height (stature), body mass index (BMI), level of education and household wealth had independent effects on age at menarche, whereas urbanresidence had no effect. Socioeconomic gradients were large:+9 years of schooling was associated with a-0.52 year decrease in age at menarche, and+2 standard deviations in household wealth with a-0.33year decrease. The impact of anthropometry was even greater:+2 standard deviations in height was associated with a-0.99 year decrease in age at menarche, and+2 standard deviations in BMI with a-1.42 yeardecrease. Northern provinces had a higher mean age at menarche than southern provinces. Compared withindependent sources, long-term trends in age at menarche, as well as their fluctuations, appeared to becorrelated with trends and fluctuations in incomeper capitaand in under-five mortality, but not withdivergent trends in adult height