CDC Growth Charts 2000

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CDC Growth Charts 2000
Centers for Disease Control and
Prevention National Center for Chronic Disease
Prevention and Health Promotion Division of
Nutrition and Physical Activity Maternal and
Child Nutrition Branch
Revised June 2002
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Training Objectives

• Science behind development of growth charts
• Rationale for including BMI-for-age
• Using BMI-for-age as a screening tool

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What growth charts are available?
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New Features of the Growth Charts

• BMI-for-age charts (2-20 years)
• 85th percentile (at risk of overweight)
  
• 3rd and 97th percentiles available
• Lower limits of length (45 vs. 49 cm) and
  height (77 vs. 90 cm) extended
• Smoothed percentile curves and z-scores
  agree
• Correction in the disjunction

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Disjunction Smoothed in New Charts
120
120
1977
2000
110
110
100
100
90
90
Length/height in cm
80
Length/height in cm
80
70
70
60
60
50
50
40
40
42
48
0
6
12
18
24
30
36
54
60
0
6
12
18
24
30
36
42
48
54
60
Age in month
Age in month
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Reference Population for CDC Growth Charts

• Racially and ethnically diverse
• Infants Birth to 36 months
• Children and Adolescents 2 to 20 years
• Breast- and formula-fed infants

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Reference Data Sets Birth to 36 Months
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Reference Data Sets 2 to 20 Years
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Exclusions from the Reference Data

• Very low birth weight (VLBW) infants (lt1500 g)
  were excluded because they have different growth
  patterns
• NHANES III weight data for 6 year olds were
  excluded to avoid an upward shift in
  weight-for-age and BMI-for-age curves

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Age-Adjusted Prevalence of
Overweight1 From NHANES I to III 2
Percent
Sex and Age Group

• 1gt95th percentile BMI-for-age
• 2 http//www.cdc.gov/nchs/products/pubs/pubd/hesta
  ts/overwght99.htm

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CDC Growth Charts Are for All
Racial and Ethnic Groups Combined

• Environmental influences appear to contribute
  to variations in growth more than genetic
  influences
• Inadequate sample data for racial- and ethnic-
  specific charts
• The effect of race and ethnicity on
  BMI-for- age is unclear

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Age Adjusted Prevalence of Low Height-for-Age by
Ethnic Groups, Children Aged 0 to 5 Years1
Percentage
Year of Visit
1 Mei, Yip and Trowbridge, Asia Pacific J Clin
Nutr 1998 7(2) 111-116
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Breast-Fed vs. Formula-Fed Infants

• Mode of infant feeding can influence growth
• New charts represent the combined growth patterns
  of breast-fed and formula-fed infants
• Working group of the World Health Organization
  (WHO) is developing growth charts for infants and
  children through age 5 using data collected on
  infants following WHO feeding recommendations

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Indicators of Nutritional Status
lt5th percentile gt95th percentile
Head circumference-for-age
Stunting/shortness length or stature-for-age
lt5th percentile
Underweight weight-for-length BMI-for-age
lt5th percentile
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Indicators of Nutritional Status
Overweight Weight-for-length BMI-for-age
gt95th percentile
Risk of overweight BMI-for-age
85th to 95th percentile
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Prevalence of Nutritional Status Indicators
New Reference Curves Compared with Old Curves
lt 2 Years Old
Change in Prevalence
Nutrition Indicator
Stunting/shortness length-for-age lt5th
1 to 2 lower
Underweight weight-for-length lt5th
1 to 2 higher
Overweight weight-for-length gt95th
2 lower for females 2 higher for males
NHANES III
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Prevalence of Nutritional Status Indicators
New Reference Curves Compared with Old Curves
Children 2 to 5 years of age
Nutrition Indicator
Change in Prevalence
Stunting/shortness stature-for-age lt5th
1 lower
3 to 4 higher
Underweight lt5th
No change for females 1 higher for males
Overweight 95th
NHANES III BMI-for-age, weight-for-stature
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What Is BMI?

• Body mass index (BMI)
• weight (kg)/height (m)2
• BMI is an effective screening tool it is not a
  diagnostic tool
• For children, BMI is age and gender specific, so
  BMI-for-age is the measure used

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Advantages of BMI-for-Age

• Provides a reference for adolescents that was not
  previously available
• Consistent with adult index so it can be used
  continuously from 2 years of age to adulthood
• Tracks childhood overweight into adulthood

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Tracking BMI-for-Age from Birth to 18 Years with
Percent of Overweight Children
who Are Obese at Age 251
Whitaker et al. NEJM 1997337869-873
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Advantages of BMI-for-Age

• BMI-for-age relates to health risks
• Correlates with clinical risk factors for
  cardiovascular disease including hyperlipidemia,
  elevated insulin, and high blood pressure
• BMI-for-age during pubescence is related to lipid
  levels and high blood pressure in middle age

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BMI-for-Age Compares Well with

• Weight-for-stature measurements 1
• Measures of body fat

Mei et al., Am J Clin Nutr 200275978-85.
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Why Use BMI-for-Age?

• Recommended by expert committees to evaluate
  overweight

• Guidelines for Overweight in Adolescent
  Preventive
• Services (Am J Clin Nutr 199459307-316)
• Obesity Evaluation and Treatment Expert
  Committee
• Recommendations (Pediatrics 1998
  Sept(102)3e 29)
• Assessment of Childhood and Adolescent Obesity
• International Obesity Task Force (Am J Clin
  Nutr 1999, 70,suppl)

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Shape of Weight-for-Stature Curve versus
BMI-for-Age Curve
95th
95th
50th
5th
50th
5th
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For Children, BMI Changes with Age
BMI
BMI
Example 95th Percentile Tracking Age
BMI 2 yrs 19.3 4 yrs 17.8 9 yrs
21.0 13 yrs 25.1
Boys 2 to 20 years
BMI
BMI
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Shape of BMI-for-Age Growth Curve Adiposity
Rebound (AR) Example Early AR Age
(mos) BMI 26 18.2
32 17.4 38
18.5 41 18.7
BMI
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BMI-for-Age Cutoffs

• gt 95th percentile Overweight
• 85th to lt 95th Risk of overweight
• percentile
• lt 5th percentile Underweight

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Performance of BMI-for-Age
as a Screening Tool

• Using the 85th and 95th percentiles as cut
  points, few children are incorrectly identified
  as over-fat but some over-fat children will be
  missed.
• It is desirable to correctly identify those
  children not at risk of overweight or overweight.

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Calculating BMI with the Metric System
Formula weight (kg)/height
(m)2 Calculation weight (kg)/
height (cm)/
height (cm) x 10,000
Example A childs weight16.9 kg and
height105.4 cm BMI 16.9 kg / 105.4 cm /
105.4 cm x 10,000 15.2
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Calculating BMI with the English System
Formula weight (lb)/height (in)2 x 703
Calculation weight (lb)/height (in)/height
(in) x 703
Example A childs weight 37 pounds, 4 ounces
and height 41 1/2 inches
(convert fractions to decimal value) BMI
37.25 lb / 41.5 in / 41.5 in x 703 15.2
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Can you see risk?

• This boy is 3 years, 3 weeks old.
• Is his BMI-for-age
• - gt85th to lt95th percentile at risk
  for overweight?

Photo from UC Berkeley Longitudinal Study, 1973
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Plotted BMI-for-Age
Measurements Age3 y 3 wks Height100.8 cm
(39.7 in) Weight18.6 kg (41
lb) BMI18.3 BMI-for-age gt95th
percentile overweight
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Can you see risk?

• This girl is 4 years, 4 weeks old.
• Is her BMI-for-age
• - gt85th to lt95th percentile at
  risk for overweight?

Photo from UC Berkeley Longitudinal Study, 1974
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Plotted BMI-for-Age
Measurements
BMI
BMI
Age 4 y 4 wks Height106.4 cm (41.9
in) Weight15.7 kg (34.5
lb) BMI13.9 BMI-for-age 10th
percentile Normal
Girls 2 to 20 years
BMI
BMI
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Can you see risk?

• This girl is 4 years old.
• Is her BMI-for-age
• - gt85th to lt95th percentile at risk for
  overweight?

Photo from UC Berkeley Longitudinal Study, 1973
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Plotted BMI-for-Age
Measurements Age4 y Height99.2 cm
(39.2 in) Weight17.55 kg
(38.6 lb) BMI17.8 BMI-for-age between 90th
95th percentile
At risk for overweight
BMI
BMI
Girls 2 to 20 years
BMI
BMI
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Accurate Measurements are Critical
5 1/2 year old boy Weight 41.5 lb Height 43
in BMI 15.8 BMI-for-age50th tile Inaccurate
height measurement 42.25 BMI16.3 BMI-for-age75t
h tile
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Interpreting the BMI-for-Age Cutoffs

• gt 95th percentile Overweight
• 85th to lt 95th Risk of overweight
• percentile
• lt 5th percentile Underweight

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Interpreting the BMI-for-Age Chart

• BMI-for-age indicates a childs weight in
  relation to his/her height for a specific age and
  gender
• Need a series of BMI plots to determine the
  growth trend
• If indices deviate from normal growth patterns,
  further assessment may be needed

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Example Sam

• Name Sam
• Weight 37 lb 4 oz (16.9 kg)
• Height 41.5 inches (105 cm)
• Age 3.5 years
• BMI 15.2

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Sams BMI Plotted on Boys BMI-for-Age Chart

• Interpretation
• Sams BMI-for-age is slightly below the 25th
  tile so it falls within the normal range.
• Of 100 boys who are the same age, fewer than 25
  have a BMI-for-age lower than Sams.

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Summary of Using BMI-for-Age

• BMI-for-age is the recommended method for
  screening overweight and underweight
• For children, BMI is age and gender
  specific for adults there are fixed cut
  points
• Accurate and periodic measurements are
  important elements of any anthropometric
  screening

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Steps to Plot BMI-for-Age

• Obtain accurate weight and height measurements
• Select the appropriate growth chart
• Record the data
• Calculate BMI
• Plot measurements
• Interpret plotted measurements

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Please visit http//www.cdc.gov/growthcharts/

• For additional training materials related
  to the growth charts
• For tools related to the growth charts
• To download the growth charts

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www.cdc.gov/growthcharts