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

Training Objectives Science behind development of growth charts Rationale for including BMI-for-age Using BMI-for-age as a screening tool 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 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 Age in month Length/height in cm Age in month Length/height in cm

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

Reference Data Sets: 2 to 20 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 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 >95 th percentile BMI-for-age >95 th percentile BMI-for-age 2 Age-Adjusted Prevalence of Overweight 1 From NHANES I to III 2 Sex and Age Group Percent

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 Years 1 Year of Visit Percentage 1 Mei, Yip and Trowbridge, Asia Pacific J Clin Nutr 1998; 7(2):

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 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 <5 th percentile Stunting/shortness length or stature-for-age Head circumference-for-age <5 th percentile >95 th percentile Underweight weight-for-length BMI-for-age

Indicators of Nutritional Status Overweight Weight-for-length BMI-for-age >95 th percentile Risk of overweight BMI-for-age 85 th to 95 th percentile

Prevalence of Nutritional Status Indicators New Reference Curves Compared with Old Curves* < 2 Years Old Nutrition Indicator Change in Prevalence Stunting/shortness length-for-age <5 th 1% to 2% lower Underweight weight-for-length <5 th * NHANES III Overweight weight-for-length >95 th 2% lower for females 2% 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/shortness stature-for-age <5 th 1% lower Underweight** <5 th 3% to 4% higher * NHANES III **BMI-for-age, weight-for-stature Overweight** 95 th No change for females 1% 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 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 from2 years of age to adulthood  Tracks childhood overweight into adulthood  Provides a reference for adolescents that was not previously available  Consistent with adult index so it can be used continuously from2 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 25 1 Whitaker et al. NEJM: 1997;337:

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  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:

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: )  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 95 th 50 th 5 th 95 th 50 th 5 th

Example: 95th Percentile Tracking Age BMI 2 yrs yrs yrs yrs 25.1 For Children, BMI Changes with Age Boys: 2 to 20 years BMI

Shape of BMI-for- Age Growth Curve: “Adiposity” Rebound (AR) Example: Early AR Age (mos) BMI Boys: 2 to 20 years BMI

BMI-for-Age Cutoffs > 95 th percentile Overweight 85 th to < 95 th Risk of overweight percentile < 5 th percentile Underweight

Using the 85 th and 95 th 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. Using the 85 th and 95 th 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 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 / cm / 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 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 - >85 th to <95 th percentile: at risk for overweight? Photo from UC Berkeley Longitudinal Study, 1973

Measurements: Age=3 y 3 wks Height=100.8 cm (39.7 in) Weight=18.6 kg (41 lb) BMI=18.3 BMI-for-age= >95 th percentile overweight Plotted BMI-for-Age Boys: 2 to 20 years BMI

Can you see risk? This girl is 4 years, 4 weeks old. Is her BMI-for-age - >85 th to <95 th 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 wks Height=106.4 cm (41.9 in) Weight=15.7 kg (34.5 lb) BMI=13.9 BMI-for-age= 10 th percentile Normal BMI

Can you see risk? This girl is 4 years old. Is her BMI-for-age - >85 th to <95 th percentile: at risk for overweight? Photo from UC Berkeley Longitudinal Study, 1973

Measurements: Age=4 y Height=99.2 cm (39.2 in) Weight=17.55 kg (38.6 lb) BMI=17.8 BMI-for-age= between 90 th –95 th percentile At risk for overweight Plotted BMI-for-Age Girls: 2 to 20 years BMI

5 1/2 year old boy Weight: 41.5 lb Height: 43 in BMI= 15.8 BMI-for-age=50 th %tile Inaccurate height measurement: BMI=16.3 BMI-for-age=75 th %tile Accurate Measurements are Critical Boys: 2 to 20 years BMI

Interpreting the BMI-for-Age Cutoffs > 95 th percentile Overweight 85 th to < 95 th Risk of overweight percentile < 5 th 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 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 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 %tileso 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

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 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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