Article

National Estimates of the Timing of Sexual Maturation and Racial Differences Among US Children

The Lifespan Health Research Center Departments of Community Health, Pediatrics, and Mathematics and Statistics, Wright State University, School of Medicine, Dayton, Ohio 45420, USA.
PEDIATRICS (Impact Factor: 5.47). 12/2002; 110(5):911-9. DOI: 10.1542/peds.110.5.911
Source: PubMed
ABSTRACT
To provide clinically meaningful, normative reference data that describe the timing of sexual maturity indicators among a national sample of US children and to determine the degree of racial/ethnic differences in these estimates for each maturity indicator.
Tanner staging assessment of sexual maturity indicators was recorded from 4263 non-Hispanic white, black, and Mexican American girls and boys aged 8.00 to 19.00 years as part of the Third National Health and Nutrition Examination Survey (NHANES III) conducted between 1988 and 1994. NHANES III followed a complex, stratified, multistage probability cluster design. SUDAAN was used to calculate the mean age and standard error for each maturity stage and the proportion of entry into a maturity stage and to incorporate the sampling weight and design effects of the NHANES III complex sampling design. Probit analysis and median age at entry into a maturity stage and its fiducial limits were calculated using SAS 8.2.
Reference data for age at entry for maturity stages are presented in tabular and graphical format. Non-Hispanic black girls had an earlier sexual development for pubic hair and breast development either by median age at entry for a stage or for the mean age for a stage than Mexican American or non-Hispanic white girls. There were few to no significant differences between the Mexican American and non-Hispanic white girls. Non-Hispanic black boys also had earlier median and mean ages for sexual maturity stages than the non-Hispanic white and Mexican American boys.
Non-Hispanic black girls and boys mature early, but US children completed their sexual development at approximately the same ages. The present reference data for the timing of sexual maturation are recommended for the interpretation of assessments of sexual maturity in US children.

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Available from: Christine Schubert, Jun 03, 2014
DOI: 10.1542/peds.110.5.911
2002;110;911-919 Pediatrics
Howard E. Kulin, Peter A. Lee, John H. Himes and Alan S. Ryan
Shumei S. Sun, Christine M. Schubert, William Cameron Chumlea, Alex F. Roche,
Among US Children
National Estimates of the Timing of Sexual Maturation and Racial Differences
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National Estimates of the Timing of Sexual Maturation and Racial
Differences Among US Children
Shumei S. Sun, PhD*; Christine M. Schubert, MS*; William Cameron Chumlea, PhD*;
Alex F. Roche, MD, PhD, DSc*; Howard E. Kulin, PhD‡; Peter A. Lee, PhD‡; John H. Himes, PhD§; and
Alan S. Ryan, PhD
ABSTRACT. Objective. To provide clinically mean-
ingful, normative reference data that describe the timing
of sexual maturity indicators among a national sample of
US children and to determine the degree of racial/ethnic
differences in these estimates for each maturity indicator.
Methods. Tanner staging assessment of sexual matu-
rity indicators was recorded from 4263 non-Hispanic
white, black, and Mexican American girls and boys aged
8.00 to 19.00 years as part of the Third National Health
and Nutrition Examination Survey (NHANES III) con-
ducted between 1988 and 1994. NHANES III followed a
complex, stratified, multistage probability cluster design.
SUDAAN was used to calculate the mean age and stan-
dard error for each maturity stage and the proportion of
entry into a maturity stage and to incorporate the sam-
pling weight and design effects of the NHANES III com-
plex sampling design. Probit analysis and median age at
entry into a maturity stage and its fiducial limits were
calculated using SAS 8.2.
Results. Reference data for age at entry for maturity
stages are presented in tabular and graphical format.
Non-Hispanic black girls had an earlier sexual develop-
ment for pubic hair and breast development either by
median age at entry for a stage or for the mean age for a
stage than Mexican American or non-Hispanic white
girls. There were few to no significant differences be-
tween the Mexican American and non-Hispanic white
girls. Non-Hispanic black boys also had earlier median
and mean ages for sexual maturity stages than the non-
Hispanic white and Mexican American boys.
Conclusion. Non-Hispanic black girls and boys ma-
ture early, but US children completed their sexual devel-
opment at approximately the same ages. The present
reference data for the timing of sexual maturation are
recommended for the interpretation of assessments of
sexual maturity in US children. Pediatrics 2002;110:911–
919; sexual maturity, Tanner stages, age at onset, second-
ary sex characteristics, race.
ABBREVIATIONS. NHES, National Health Examination Survey;
HHANES, Hispanic Health and Nutrition Examination Survey;
NHANES III, Third National Health and Nutrition Examination
Survey.
A
ssessment of the onset and progression of
sexual maturation are important in pediatrics
because this information has immediate clin-
ical application in the interpretation of endocrine and
growth status.
1–4
Criteria describing the stages of
sexual maturity indicators in boys and girls are well
established.
5–7
Sexual maturity assessments are
meaningful, however, when the age of a child who is
entering a stage or the age of a child who is already
in a stage can be compared with suitable reference
data for sexual maturity stages in normal healthy
peers. Normative references for sexual maturity lev-
els of current US children have been few, and most
are outdated or limited because of the composition
and ages of the samples involved.
8,9
Recent concern
about the possible early onset of puberty in US chil-
dren
9–11
has highlighted the need for current norma-
tive national reference data to facilitate the interpre-
tation of sexual maturity assessments.
Sexual maturity status of US children from nation-
ally representative samples is available. The timing
of sexual maturity of non-Hispanic white and black
children from the National Health Examination Sur-
vey (NHES) was documented 20 years ago, when
earlier maturation in non-Hispanic black girls than
white girls was noted.
3,4
Sexual maturity data for
Mexican American children from the Hispanic
Health and Nutrition Examination Survey
(HHANES) were reported approximately a decade
ago.
12
However, these NHES and HHANES data
were from children only as young as 12.00 and 10.00
years, respectively, and neither of these is young
enough to provide estimates of early sexual matura-
tion.
13
Recently, sexual maturity data were collected from
a national probability sample of US children aged
8.00 to 19.00 years as part of the Third National
Health and Nutrition Examination Survey
(NHANES III) conducted from 1988 to 1994. Infor-
mation on the prevalence of sexual development of
boys using these NHANES III data has been report-
ed,
11
including estimates of the median ages of tran-
sition from one Tanner stage to the next. The aims of
the present analysis were 1) to estimate the median
age at entry for a stage in tabular format, the ages at
which 25%, 50%, and 75% of children transitioned
From *The Lifespan Health Research Center Departments of Community
Health, Pediatrics, and Mathematics and Statistics, Wright State University,
School of Medicine, Dayton, Ohio; ‡Pennsylvania State College of Medicine,
Hershey Medical Center, Hershey, Pennsylvania; §School of Public Health,
University of Minnesota, Minneapolis, Minnesota; and Ross Products Di-
vision of Abbott Laboratories, Columbus, Ohio.
Received for publication Nov 9, 2001; accepted Mar 18, 2002.
Reprint requests to (S.S.S.) Lifespan Health Research Center, Department of
Community Health, Wright State University School of Medicine, 3171 Re-
search Blvd, Kettering, OH 45420. E-mail: shumei.sun@wright.edu
PEDIATRICS (ISSN 0031 4005). Copyright © 2002 by the American Acad-
emy of Pediatrics.
PEDIATRICS Vol. 110 No. 5 November 2002 911
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from stage 1 to stage 2 in graphical format, and the
mean age for being in a stage for each sexual matu-
rity indicator in the NHANES III for non-Hispanic
white, black, and Mexican American girls and boys
and 2) to determine racial/ethnic differences in these
estimates for each maturity indicator. Median age at
entry for a stage is the age when 50% of the children
entered that stage. The mean age for being in a stage
is the average ages for all children in that stage at the
time of examination. It is anticipated that median age
at entry would be earlier than the mean age for being
in a stage. These results provide clinically meaning-
ful, normative reference data that describe the timing
of sexual maturity indicators among a national sam-
ple of US children.
METHODS
Sample
The data are from the NHANES III conducted by the National
Center for Health Statistics between 1988 and 1994.
14,15
NHANES
III used a complex, stratified, multistage probability cluster design
to obtain representative samples of the noninstitutionalized US
civilian population.
16,17
Like other national health surveys, the
NHANES III sample represented the total US civilian noninstitu-
tionalized population that was 2 months old or older at the time
the data were collected.
14
Assessment of sexual maturity indica-
tors were recorded from 4263 children aged 8.00 to 19.00 years.
The number of children in each age, gender, and racial/ethnic-
specific group used in this analysis is presented in Table 1. In
NHANES III, there was intentional oversampling of those aged
8.00 to 19.00 years and of Mexican Americans and non-Hispanic
blacks to increase the reliability of estimates for these groups.
Sexual Maturity Stages
Sexual maturity of each child was assessed by physicians dur-
ing the NHANES III physical examination. These physicians re-
ceived special standardized training. Written descriptions and
photographs describing the stages of the sexual maturity indica-
tors used during training were available for reference in the ex-
amination centers. The details of this training are documented.
14
Sexual maturity stages based on the recommendations of Tan-
ner
6,7
were assigned to each maturity indicator, ie, pubic hair in
each gender, breast development in girls, and genital develop-
ment (penis, testes, and scrotum) in boys. Each maturity indicator
has 5 stages that can be assigned from stage 1, representing
immaturity, to stage 5, indicating full maturity. Details of the
criteria used in NHANES III characterizing the appearance of each
Tanner stage for each sexual maturity indicator have been de-
scribed and reported extensively.
7,12,18
The notation used in this
report for each maturity indicator contains the initial letters as
follows: pubic hair (PH), breast development (B), and genital
development (G). Thus, Tanner stage 2 for genital development in
boys is indicated as G2.
Data Analysis
SUDAAN
19
was used to calculate means, standard errors, and
design effects for each stage in each indicator using the final
adjusted individual weight and incorporating the complex sam-
pling design specifying the strata and primary sampling units.
Mean ages for being in each of the stages for each sexual maturity
indicator were calculated by gender and race. The sample sizes in
the present study were larger than that required for reliable esti-
mates for the total population.
20
Estimates of median age of entry into a stage for each indicator
were computed in several steps. First, the proportion of children
who entered a specified stage within each age group for a given
maturity indicator was computed using PROC CROSSTAB of
SUDAAN,
19
which adjusts for the individual sampling weights
and the design effects of the complex sampling design. In the
probit analysis, the data were grouped into 3-month age groups
starting at 8 years of age. Sex- and race-specific probit analyses
were applied to proportions across age groups using SAS 8.2.
21
In
the probit analysis, the proportion of children who entered a
maturity stage is transformed into y, a normal equivalent devi-
ate, ie, P ⫽兰
⫺⬁
y
f(
)d
, where y a bx and x is the age in months
and a and b are the parameters to be estimated from the data. The
median age at entry is estimated when P is at 50%. Therefore,
median age at entry into a stage is the age at which 50% of the
children entered a maturity stage. The fiducial limits of the me-
dian age at entry into a stage were computed using Fiellers
theorem.
22
The ranges for the fiducial limits indicate the level of
precision about these estimated median ages from the probit
analysis. The more narrow the range about the median, the higher
the precision of the estimated age.
Because comparisons were made among 3 racial groups within
a gender, the fiducial limits for each median age for each group
were calculated at a 98.3% confidence level. The 3 sets of fiducial
limits yielded a comparison-wise confidence level of 95%, ie, (1
) 0.983 and (1
)
3
0.95. Intervals were adjusted for
multiple comparisons between races for each gender, stage, and
sexual maturity indicator to test for significant differences with an
overall
of 0.05. In addition to the median age at entry (50th
percentile), ages at the onset of puberty at the 25th and 75th
percentiles indicating when 25% and 75% of children transitioned
from stage 1 to stage 2 were obtained for each maturity indicator.
It is anticipated that median age at entry for a maturity stage
will be earlier than the mean age of all children who are in a
specific maturity stage. This is because age at entry for a stage is
the age at which an individual child progresses from one stage to
the next, whereas mean age for being in a stage is the average ages
at examination of all individual children who were assessed as
being in a stage. Some children may be in a given stage for some
time.
RESULTS
The results are presented for each sexual maturity
indicator for girls and boys separately for each race
in the following sections. The median ages for entry
for a stage and the mean ages for specific stages for
each maturity indicator were calculated with adjust-
TABLE 1. Sample Sizes for Each Age Group for Boys and Girls by Race/Ethnic Group
Age
(Years)
Boys Girls
Whites Blacks Mexican
Americans
Whites Blacks Mexican
Americans
88.99 61 71 81 52 71 82
99.99 70 96 85 76 87 78
1010.99 65 97 89 61 82 81
1111.99 62 92 101 62 79 93
1212.99 42 68 62 45 82 73
1313.99 39 48 64 50 71 67
1414.99 43 70 47 48 56 69
1515.99 33 71 62 57 56 49
1616.99 43 65 61 43 72 57
1717.99 39 61 65 52 61 66
1819.00 40 59 66 48 71 48
Total 537 798 783 594 788 763
912 TIMING OF SEXUAL MATURATION AND RACIAL DIFFERENCES IN US CHILDREN
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ment of individual sampling weights and the design
effects. Therefore, these median and mean ages rep-
resent national estimates. The standard errors for the
mean ages for specific stages for the indicators
ranged from 0.08 to 0.34 years. By approximately
16.5 years, most US girls and boys were sexually
mature, ie, they had attained stage 5 for all indica-
tors.
Sexual Maturation in Girls
Age at Entry
The median age at entry and the fiducial limits, a
measure of the precision of the estimated median
age, for pubic hair and breast development stages are
presented in Table 2. The median age at the onset of
pubic hair development was approximately 9.4 years
for non-Hispanic black girls, approximately 10.6
years for non-Hispanic white girls, and approxi-
mately 10.4 years Mexican American girls. The ages
when 25%, 50%, and 75% of the girls entered stage 2
from stage 1 for pubic hair were 8.3, 9.5, and 10.6
years, respectively, for non-Hispanic blacks; 9.7, 10.6,
and 11.5