Age at Thelarche and Hazard Ratios by BMI Percentile During Follow-Up, Race/Ethnicity and Site

StrataUnadjusted Age (in Years) at Thelarche From Kaplan-Meier Survival AnalysisaAdjusted Likelihood of Thelarche By End of Follow-up From AFT Modelb
95% CIHazard Ratio95% CI
nObservedCensoredMedianMeanSETime RatioLowerUpperLowerUpperP value
All girls123910392009.409.260.04
BMI percentile group during follow-upc
 Non-Hispanic white420355659.709.620.<.0001
 New York City416330869.
 San Francisco Bay Area444388569.809.760.
  • a Girls who did not reach thelarche before end of follow-up are censored.

  • b Hazard ratios and 95% confidence intervals calculated as described by Carroll.8

  • c For girls who were breast stage 2+ at enrollment, BMI% during follow-up is BMI% at enrollment. For girls in whom breast stage 2+ was first observed during the study, BMI% during follow-up is the BMI% at the last examination with data before thelarche. For girls who had not attained breast stage 2+ by the end of follow-up, BMI% during follow-up is the BMI% at their last examination.