Table 3.

Relation of Menarcheal Age to Childhood (Pre-Menarcheal) Levels of Various Characteristics

	Menarcheal Age (y)			Correlation with Menarcheal Agea	Odds Ratio (1 Z-Score change)b
	< 12	12–13.4	≥ 13.5
Whites
N	194	364	213
BMI (kg/m2)	17.8c	16.7	16.1	-0.26*
BMI-for-age Z	0.37	-0.10	-0.39	-0.26*	2.0* (1.6–2.5)
Weight (kg)	32.0	28.9	26.9	-0.31*
Weight-for-age Z	0.32	-0.25	-0.60	-0.32*	2.2* (1.8–2.8)
Height (cm)	132	130	128	-0.26*
Height-for-age Z	0.17	-0.28	-0.54	-0.27*	2.0* (1.6–2.5)
Triceps skinfold thickness (mm)	16	14	14	-0.20*
Blacks
N	121	174	113
BMI (kg/m2)	17.6	16.6	16.4	-0.23*
BMI-for-age Z	0.34	-0.15	-0.29	-0.26*	2.1* (1.5–3.0)
Weight (kg)	33.1	30.0	29.0	-0.31*
Weight-for-age Z	0.46	-0.10	-0.38	-0.30*	2.5* (1.8–3.6)
Height (cm)	135	132	130	-0.29*
Height-for-age Z	0.51	0.06	-0.28	-0.27*	2.6* (1.8–3.7)
Triceps skinfold thickness (mm)	13	12	11	-0.17*

^a Spearman correlation coefficients have been adjusted for examination age; ^b Odds ratios, calculated in logistic regression models that control for examination age, summarize the increased risk for early (<12 y) vs later (≥ 12 y) menarche associated with a Z-score difference of 1 unit. For example, the odds that a white girl with a BMI-for-age Z of +0.5 would experience menarche by age 12 y was 2.0-fold higher than for a girl with a Z-score of -0.5; ^c Mean levels have been adjusted for the difference in examination ages across the 3 groups using linear regression. H₀: Spearman correlation = 0 or odds ratio = 1: * p < 0.001