Relation of age at menarche to race, time period, and anthropometric dimensions: the Bogalusa Heart Study.

OBJECTIVE To assess secular trends in menarcheal age between 1973 and 1994 and to determine whether childhood levels of height, weight, and skinfold thicknesses can account for racial (white/black) differences in menarcheal age. METHODS Data from 7 cross-sectional examinations of school-aged children, with menarcheal age obtained through interviews, were used for both cross-sectional (11 218 observations) and longitudinal (n = 2058) analyses. In the latter analyses, the baseline examination was performed between ages 5.0 and 9.9 years, and the mean follow-up was 6 years. RESULTS Black girls experienced menarche, on average, 3 months earlier than did white girls (12.3 vs 12.6 years), and during the 20-year study period, the median menarcheal age decreased by approximately 9.5 months among black girls versus approximately 2 months among white girls. As compared with 5- to 9-year-old white girls, black girls were taller and weighed more, characteristics that were predictive of a relatively early (before age 11.0 years) menarche. However, even after adjustment for weight, height, and other characteristics, the rate of early menarche remained 1.4-fold higher among black girls than among white girls. CONCLUSIONS Additional study of the determinants of menarcheal age is needed, as the timing of pubertal maturation may influence the risk of various diseases in adulthood.