. Author manuscript; available in PMC: 2012 Aug 1.

Published in final edited form as: Environ Res. 2011 Jun 12;111(6):831–837. doi: 10.1016/j.envres.2011.05.016

Table 2.

Mean age at menarche (95% confidence interval [CI]) and the percentage of menarche <12 or <11 years by PBDE quartiles and other demographic characteristics in adolescent girls in the NHANES 2003–2004

	Age at Menarche^* Mean (95% CI)	Menarche <12 years (%)	Menarche <11 years (%)
Total	12.1 (11.9, 12.3)	24.0	6.0
∑BDE Concentrations (ng/g lipid) ^†
Quartile 1 (<23.3)	12.4 (12.1, 12.7)	10.0	1.7
Quartile 2 (23.3-)	12.1 (11.6, 12.5)	24.9	7.8
Quartile 3 (44.7-)	12.0 (11.6, 12.3)	24.6	6.3
Quartile 4 (≥79.8)	12.1 (11.7, 12.4)	35.8	8.1
Age (years)^‡
12–15	11.8 (11.6, 12.0)	30.2	10.1
16–19	12.4 (12.3, 12.6)	17.6	1.7
Race/ethnicity
Non-Hispanic Whites	12.2 (12.0, 12.3)	21.8	2.5
African Americans	12.1 (11.7, 12.4)	29.0	11.2
Mexican Americans and others	11.9 (11.5, 12.3)	27.7	13.8
U.S. Born
Yes	12.1 (11.9, 12.3)	24.3	5.9
No	12.4 (11.6, 13.2)	19.3	7.9
Poverty income ratio
<1	12.3 (12.0, 12.6)	20.8	4.8
1-	12.0 (11.5, 12.5)	24.1	10.0
2-	12.4 (11.9, 12.9)	19.2	2.8
3-	12.0 (11.7, 12.3)	27.6	5.9

Excluding those who had not experienced menarche (n=17 in unweighted sample)

^†

P<0.05 for the comparison of the percentage of menarche <12 years by quartiles

^‡

P<0.05 for the comparison of mean age at menarche by age groups