CDC Growth Charts 2000

Centers for Disease Control and PreventionNational Center for Chronic Disease Prevention and Health Promotion

Division of Nutrition and Physical Activity Maternal and Child Nutrition Branch

Revised June 2002

Training Objectives

• Science behind development of growth charts

• Rationale for including BMI-for-age

• Using BMI-for-age as a screening tool

What growth charts are available?

• 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

New Features of the Growth Charts

Disjunction: Smoothed in New Charts

40

50

60

70

80

90

100

110

120

0 6 12 18 24 30 36 42 48 54 60Age in month

Leng

th/h

eigh

t in

cm

40

50

60

70

80

90

100

110

120

0 6 12 18 24 30 36 42 48 54 60Age in month

Leng

th/h

eigh

t in

cm

1977 2000

• Racially and ethnically diverse

• Infants: Birth to 36 months

• Children and Adolescents: 2 to 20 years

• Breast- and formula-fed infants

Reference Population for CDC Growth Charts

Reference Data Sets: Birth to 36 Months

Weight-for-Length

Weight

Length

Head Circum

MO/WI Natality National Natality PedNSS

Fels NHANES III ('88-'94) NHANES II ('76-'80)

NHANES I ('71-'74)

B 3 6 9 12 15 18 21 24 27 30 33 36 Age in Months

Reference Data Sets: 2 to 20 Years

Weight/BMI

Stature

NHANES III ('88-'94) NHANES II ('76-'80) NHES II ('63-65)

NHES III ('66-'70) NHES II ('63-'65)

2 4 6 8 10 12 14 16 18 20 Age in Years

Exclusions from the Reference Data

• Very low birth weight (VLBW) infants (<1500 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

1>95th percentile BMI-for-age 2

http://www.cdc.gov/nchs/products/pubs/pubd/hestats/overwght99.htm

Age-Adjusted Prevalence of Overweight1 From NHANES I to III 2

0

5

10

15

20

Boys 6-11 y Boys 12-17 y Girls 6-11 y Girls 12-17 y

NHANES I I I I I I

Sex and Age Group

Perc

ent

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

Age Adjusted Prevalence of Low Height-for-Age by Ethnic Groups, Children Aged 0 to 5 Years1

0

5

10

15

79 80 81 82 83 84 85 86 87 88 89 90 91 92 93

WhiteAsian

Year of Visit

Perc

enta

ge

1 Mei, Yip and Trowbridge, Asia Pacific J Clin Nutr 1998; 7(2): 111-116

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

Indicators of Nutritional Status

<5th percentileStunting/shortness length or stature-for-age

Head circumference-for-age

<5th percentile

<5th percentile>95th percentile

Underweight weight-for-length BMI-for-age

Indicators of Nutritional Status

Overweight Weight-for-length BMI-for-age

>95th percentile

Risk of overweight BMI-for-age

85th to 95th percentile

Prevalence of Nutritional Status Indicators New Reference Curves Compared with Old

Curves*

< 2 Years OldNutrition Indicator Change in Prevalence

Stunting/shortnesslength-for-age <5th

1% to 2% lower

Underweightweight-for-length <5th

* NHANES III

Overweightweight-for-length >95th

2% lower for females2% higher for males

1% to 2% higher

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/shortnessstature-for-age <5th 1% lower

Underweight** <5th 3% to 4% higher

* NHANES III**BMI-for-age, weight-for-stature

Overweight** 95th No change for females1% higher for males

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

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

Tracking BMI-for-Age from Birth to 18 Years with Percent of Overweight Children who Are Obese at Age

251

16 15 12 11 10 917 19

55

7567

26

52

69

8377

36

0

20

40

60

80

100

Birth 1 to 3 3 to 6 6 to 10 10 to 15 15 to 18Age of child (years)

% o

bese

as

adul

tsBMI < 85th BMI >=85th BMI >=95th

Whitaker et al. NEJM: 1997;337:869-873

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

• Weight-for-stature measurements 1

• Measures of body fat

BMI-for-Age Compares Well with

Mei et al., Am J Clin Nutr 2002;75:978-85.

Why Use BMI-for-Age?• Recommended by expert committees to

evaluate overweight

Guidelines for Overweight in Adolescent Preventive

Services (Am J Clin Nutr 1994;59:307-316) Obesity Evaluation and Treatment: Expert Committee Recommendations (Pediatrics 1998 Sept;(102)3:e 29) Assessment of Childhood and Adolescent Obesity: International Obesity Task Force (Am J Clin Nutr 1999, 70,suppl)

Shape of Weight-for-Stature Curve versus BMI-for-Age Curve

10

15

20

25

30

35

24 72 120 168 216Age (months)

BM

I

05

101520253035

80 90 100 110 120 130Stature (cm)

Wei

ght (

kg)

95th

50th

5th

95th

50th

5th

Example: 95th Percentile Tracking Age BMI

2 yrs 19.3 4 yrs 17.8 9 yrs 21.013 yrs 25.1

For Children, BMI Changes with Age

Boys: 2 to 20 years

BMI BMI

BMI BMI

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

Boys: 2 to 20 years

BMI BMI

BMIBMI

BMI

BMI-for-Age Cutoffs

> 95th percentile Overweight

85th to < 95th Risk of overweight percentile

< 5th percentile Underweight

• 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.

Performance of BMI-for-Age as a

Screening Tool

Formula: weight (kg)/[height (m)]2

Calculation: [weight (kg)/ height (cm)/ height (cm)] x 10,000

Calculating BMI with the Metric System

Example: A child’s weight=16.9 kg and height=105.4 cm

BMI = [16.9 kg / 105.4 cm / 105.4 cm] x 10,000 = 15.2

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 child’s 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

Can you see risk?

• This boy is 3 years, 3 weeks old.

• Is his BMI-for-age

- >85th to <95th percentile: at risk for overweight?

Photo from UC Berkeley Longitudinal Study, 1973

Measurements: Age=3 y 3 wksHeight=100.8 cm

(39.7 in)Weight=18.6 kg

(41 lb)BMI=18.3 BMI-for-age=

>95th percentile overweight

Plotted BMI-for-Age

Boys: 2 to 20 years

BMI BMI

BMI BMI

Can you see risk?

• This girl is 4 years, 4 weeks old.

• Is her BMI-for-age

- >85th to <95th percentile: at risk for overweight?

Photo from UC Berkeley Longitudinal Study, 1974

Measurements:

Plotted BMI-for-Age

Girls: 2 to 20 years

Age= 4 y 4 wksHeight=106.4 cm (41.9 in)Weight=15.7 kg

(34.5 lb)BMI=13.9BMI-for-age= 10th percentile Normal

BMI BMI

BMIBMI

Can you see risk?

• This girl is 4 years old.• Is her BMI-for-age

- >85th to <95th percentile: at risk for overweight?

Photo from UC Berkeley Longitudinal Study, 1973

Measurements: Age=4 yHeight=99.2 cm

(39.2 in)Weight=17.55 kg (38.6 lb)BMI=17.8BMI-for-age= between 90th –95th percentile At risk for overweight

Plotted BMI-for-Age

Girls: 2 to 20 years

BMI

BMIBMI

BMI

5 1/2 year old boyWeight: 41.5 lbHeight: 43 inBMI= 15.8BMI-for-age=50th %tileInaccurate height measurement: 42.25BMI=16.3BMI-for-age=75th %tile

Accurate Measurements are Critical

Boys: 2 to 20 years

BMI BMI

BMI BMI

Interpreting the BMI-for-Age Cutoffs

> 95th percentile Overweight

85th to < 95th Risk of overweight percentile

< 5th percentile Underweight

Interpreting the BMI-for-Age Chart • BMI-for-age indicates a child’s 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

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

Sam’s BMI Plotted on Boy’s BMI-for-Age Chart

Interpretation:• Sam’s 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 Sam’s.

Boys: 2 to 20 years

BMI BMI

BMI BMI

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

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

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

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

www.cdc.gov/growthcharts