Is sexual maturity occurring earlier among U.S. children?

To compare the onset and completion of sexual maturation among U.S. children between 1966 and 1994.

Tanner stages were from 3042 non-Hispanic white boys, 478 black boys, 2625 white girls, and 505 black girls (NHES 1966-70), from 717 Mexican-American boys and 712 Mexican-American girls (HHANES 1982-84) and from 259 non-Hispanic white boys, 411 black boys, 291 white girls, 415 black girls, 576 Mexican-American boys and 512 Mexican-American girls (NHANES III 1988-1994). Proportions of entry into a stage, probit analysis estimated medians and selected percentiles for ages at entry were calculated using SUDAAN.

NHANES III (1988-1994) non-Hispanic white boys entered stage 2, 3, and 4 genital development and stages 3 and 4 pubic hair earlier than NHES (1966-1970) white boys, but they entered stage 5 genital development significantly later. NHANES III (1988-1994) Mexican-American boys were in stage 2, 3 and 4 genital development earlier than HHANES (1982-1984) boys, but entry into stage 5 genital and pubic hair development was not significant. NHANES III (1988-1994) white girls entered stage 5 pubic hair later than NHES (1966-1970) white girls. NHANES III (1988-1994) Mexican-American girls entered stage 2 breast and pubic hair development earlier than HHANES (1982-1984) girls, entered stage 4 breast and pubic hair development earlier but entered stage 5 pubic hair later than the HHANES (1982-1984) girls.

Persuasive evidence of a secular trend toward early maturation is not found between 1966 and 1994 in non-Hispanic black boys and non-Hispanic black and white girls. Some evidence of this trend is found in non-Hispanic white boys between 1966 and 1994 and in Mexican-American boys and girls between 1982 and 1994.