Age of puberty: Data from the United States of America

In an attempt to determine whether the secular trend toward an earlier onse t of puberty has continued over recent decades in the United States of Amer ica, published reports concerning the age of attainment of pubertal events have been reviewed. Such reports are very limited and vary in both design a nd inclusive ages of study subjects. Among females, two recent large cross- sectional studies indicate that fifty percent of females in the United Stat es attain Tanner breast stage 2 at 9.5 to 9.7 years of age. This is younger than previously thought, although adequate earlier studies of girls in the United States are not available for comparison. These two studies also ind icate that about 14% of girls attain Tanner stage 2 while 8 years of age; o ne study extends earlier reporting that about 6% exhibit onset of breast de velopment while 7 years of age. There is no evidence that the age of menarc he or the attainment of adult (Tanner 5) breast development has decreased o ver the past 30 years. The data also suggest an earlier onset of Tanner sta ge 2 pubic hair but no change in attainment of stage 5. Among males, pubic hair may be appearing at younger ages, but data are inadequate or too incon sistent to allow firm interpretation. The lack of standardization of genita l criteria of pubertal onset in the male makes any conclusions regarding se cular trends impossible. In summary, earlier secular trends over recent dec ades related to better health, improved nutrition or socio-economic status, or any putative influence by endocrine disrupters cannot be verified.