Use of the WHO Growth Standards in the United States APHA November 5, 2007 Laurence M. Grummer-Strawn Nutrition Branch Division of Nutrition, Physical Activity, and Obesity

Background NCHS 1977 growth reference used worldwide until 2000 CDC 2000 growth reference currently in use across the U.S. for children aged 0-19.9 years April 2006, WHO released a new international growth standard for children aged 0-4.9 years

Recommendations for the U.S. Expert panel was convened June 29-30, 2006 Sponsored by CDC/NIH/AAP Considered Rationale for standard vs. reference Use of international data for the U.S. Implications for breastfed as well as formula-fed infants Methods in construction of both curves Statistical comparisons between the curves Practicalities of using multiple charts

Rationale for standard vs. reference Because clinicians make decisions on health of the child, standard may be more appropriate Qualitative research has shown that clinicians understand the use of a standard But communication to parents about what a given percentile means would be difficult

Use of international data for the U.S. Data on children from India, Ghana, Norway, Brazil & Oman Data show that difference across countries are small U.S. is a mixture of many nationalities But communication to parents about why these comparisons are appropriate may be difficult

Implications for breastfed as well as formula-fed infants Concerns over using breastfeeding standard for formula-fed children But others concerned over using formula-fed reference for breastfed children (2/3 in CDC charts not breastfed beyond 3 months.) AAP has said that breastfed child is the norm Intake of breastfed child is used for setting DRIs Separate charts for breast- and formula-fed babies are impractical

Methods in construction of both curves CDC 2000 growth reference Describes growth in the U.S. in the 1970s and 1980s Based on nationally representative data VLBW infants excluded 4 references: Weight-for-age 0-20 yrs Length-for-age 0-3 yrs/Stature-for-age 2-20 yrs Weight-for-length & weight-for-stature 0-6 yrs BMI-for-age 2-20 yrs

Key differences (Birth-2 yrs) WHO Longitudinal data Feeding requirements Exclusive/predominant breastfeeding > 4 months Complementary feeding by 6 months Continued breastfeeding > 12 months Frequent data collection biweekly 0-8 weeks Monthly 2-12 months Bimonthly 14-24 months 18,973 observations CDC Cross-sectional data No feeding requirements ~50% ever breastfed ~33% breastfeeding at 3 months No data between birth and 3 months mathematical models used 4,697 observations

Smaller differences at 2-5 yrs WHO Cross-sectional data Feeding requirements Breastfed at least 3 months Stop at age 5 Overweight children (above +2SD) excluded 6,669 observations CDC Cross-sectional data No feeding requirements Continuous with curves up to age 20 No data exclusions 9,894 observations

Statistical comparisons between the curves More infants will “fall off” WHO weight-for-age charts up to age 3 months but fewer will “fall off” from 3-18 months Fewer infants would be below 5th percentile on WHO weight-for-age charts More infants would be above 95th percentile on WHO weight-for-length or BMI-for-age charts More infants would be below 5th percentile on WHO length-for-age charts

Cutoffs WHO recommends cutoffs at -2 SD (2.3rd percentile) and +2SD (97.7th percentile) In U.S., 5th and 95th percentiles more commonly used Because WHO standard measured healthy children under optimal conditions, the more extreme cutoffs may be appropriate Prevalence of stunting and overweight more similar using WHO cutoffs on WHO charts

Practicalities of using multiple charts WHO curves only extend to age 5: Clinicians will need to use CDC charts for older children If WHO curves adopted for 5 years, need to use 3 sets of curves: 0-2 years: WHO length-based 2-5 years: WHO stature-based 5-20 years: CDC stature-based If WHO curves adopted for 2 years, need to use 2 sets of curves: 2-20 years: CDC stature-based

Next steps AAP voted to support the WHO growth charts for birth to 24 months CDC statement is in process of clearance CDC developing supportive tools: “Clinic-friendly” charts Interactive web-based training modules