Secular trend of pubertal development in Chile

The secular trend of pubertal development in Chile is analysed on the basis of three cross-sectional studies performed in 1887, 1940 and 1970.A tendency for menarche to occur at earlier ages is observed. There is a rate of decrease of 0·066 years per decade in the period between 1887 and 1940 and of 0·29 years per decade in the last 30 years.In 1970 girls aged 10 to 17 years were taller than those in 1940 at similar socioeconomic levels. In weight, the effect of socioeconomic level seems important, thus in the sample of 1940 girls in the higher socioeconomic level were the heaviest and in the sample of 1970 both socioeconomic levels presented similar weight although the well-off sample was taller.The weight/height³ index clearly shows two effects: first, that girls in 1970 had a lower index than those in 1940. Second, the effect of socioeconomic level was not the same in 1940 and 1970; in the former year the low socioeconomic groups had a lower index than that of high socioeconomic groups, whereas the reverse was found in 1970.