TABLE 2

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
 >95th227195328.508.440.100.860.840.883.202.673.84<.0001
 85th–94.9th205181248.708.690.110.890.870.912.602.183.09<.0001
 50th–84.9th394330649.209.230.070.930.910.951.821.592.07<.0001
 <50th4113337810.109.990.071.001.00
Race/Ethnicity
 Non-Hispanic white420355659.709.620.061.061.041.080.620.540.72<.0001
 Asian575079.709.920.151.041.001.080.720.560.94.0428
 Hispanic371310619.309.230.081.051.031.070.690.600.81<.0001
 Black391324678.808.760.081.001.00
Site
 New York City416330869.109.030.081.001.00
 Cincinnati379321588.908.880.080.940.920.971.581.371.81<.0001
 San Francisco Bay Area444388569.809.760.061.031.011.050.770.660.90.0028
  • 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.