Reference Population: Standard Normal Curve 95 th 5 th 50 th Percentile.
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Transcript of Reference Population: Standard Normal Curve 95 th 5 th 50 th Percentile.
Reference Population: Standard Normal Curve
Reference Population: Standard Normal Curve
95th5th
50th Percentile
Indicators of Nutritional StatusIndicators of Nutritional Status
<5th percentileStunting/shortness length or height-for-age
Head circumference-for-age
<5th percentile
<5th percentile>95th percentile
Underweight weight-for-length BMI-for-age
Indicators of Nutritional StatusIndicators of Nutritional Status
Overweight Weight-for-length BMI-for-age
>95th percentile
Risk of overweight BMI-for-age
85th to 95th percentile
Reference Data Sets: Birth to 36 Months 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-'79)
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 Reference Data Sets: 2 to 20 Years
Weight/BMI
Stature
NHANES III ('88-'94) NHANES II ('76-'79) NHANES I ('71-'74)
HES III ('66-'70) HES II ('63-'65)
2 4 6 8 10 12 14 16 18 20
Age in Years
Exclusions from the Reference DataExclusions from the Reference Data
• 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 and BMI-for-age curves
• 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 and BMI-for-age curves
*>95th percentile BMI-for-age 1 Troiano et al, Arch Pediatr Adolesc Med 1995: 149: 1085-1091.*>95th percentile BMI-for-age 1 Troiano et al, Arch Pediatr Adolesc Med 1995: 149: 1085-1091.
Age-Adjusted Prevalence of Overweight* From NHANES I to III1
Age-Adjusted Prevalence of Overweight* From NHANES I to III1
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 GroupSex and Age Group
Perc
en
tP
erc
en
t
CDC Growth Charts Are for All Racial and Ethnic Groups Combined
CDC Growth Charts Are for All Racial and Ethnic Groups Combined
• The effect of race and ethnicity on growth is controversial
• Inadequate sample data for racial- and ethnic- specific charts
• Environmental influences appear to contribute to variations in growth but more research is needed
Age Adjusted Prevalence of Low Height-for-Age by Ethnic Groups, Children Aged 0 to 5 Years1
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 Year of Visit
Perc
en
tag
e
1 Yip and Mei, 1995
Breast-Fed vs. Formula-Fed Infants 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
• Separate charts are not recommended
• Working group of the World Health Organization (WHO) is collecting data on infants following the WHO feeding recommendations to develop charts for infants and children through age 5.
• Mode of infant feeding can influence growth
• New charts represent the combined growth patterns of breast-fed and formula-fed infants
• Separate charts are not recommended
• Working group of the World Health Organization (WHO) is collecting data on infants following the WHO feeding recommendations to develop charts for infants and children through age 5.
Disjunction: Smoothed in New ChartsDisjunction: 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
Len
gth
/heig
ht
in c
m
40
50
60
70
80
90
100
110
120
0 6 12 18 24 30 36 42 48 54 60Age in month
Len
gth
/heig
ht
in c
m
Old New
• Racially and ethnically diverse
• Birth to 36 months: nationally representative
• Breast-fed and formula-fed infants
• Racially and ethnically diverse
• Birth to 36 months: nationally representative
• Breast-fed and formula-fed infants
Reference Population for CDC Growth Charts
Reference Population for CDC Growth Charts
New Reference Curves Compared with Old Curves*
Prevalence of Nutrition Indicators
New Reference Curves Compared with Old Curves*
Prevalence of Nutrition IndicatorsBirth to 36 Months
Nutrition Indicator Change in Prevalence
Stunting/shortnesslength-for-age <5th
2% to 4% lower from 6-24 mos
Underweightweight-for-length <5th
* NHANES III, PedNSS, WHO
Overweightweight-for-length >95th
Same
3% to 5% higher
New Reference Curves Compared with Old Curves*
Prevalence of Nutrition Indicators
New Reference Curves Compared with Old Curves*
Prevalence of Nutrition IndicatorsChildren 2 to 5 years of age
Nutrition Indicator Change in Prevalence
Stunting/shortnessheight-for-age <5
2% to 3% lower
Underweight** <5 3% to 5% higher
* NHANES III, PedNSS, WHO**BMI-for-age, weight-for-stature
Overweight** 95th 3% to 5% higher
Charts extend to 20 years
3rd and 97th percentiles available
Lower limits of length (45 vs. 49 cm) and height (77 vs. 90 cm) extended
BMI-for-age charts (2-20 years) added
85th percentile (at risk of overweight) added
Charts extend to 20 years
3rd and 97th percentiles available
Lower limits of length (45 vs. 49 cm) and height (77 vs. 90 cm) extended
BMI-for-age charts (2-20 years) added
85th percentile (at risk of overweight) added
New in the CDC Growth ChartsNew in the CDC Growth Charts
What Is BMI?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-AgeAdvantages of BMI-for-Age
Provides a reference for adolescents that was not previously available
Consistent with adult standards so 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 standards so 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
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 18
Age of child (years)
% o
be
se
as a
du
lts
BMI < 85th BMI >=85th BMI >=95th
Whitaker et al. NEJM: 1997;337:869-873
Advantages of BMI-for-AgeAdvantages 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
Why Use BMI-for-Age?Why Use BMI-for-Age?
• Recommended by expert committees to evaluate overweight
• 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 Growth Curves: Weight-for-Stature versus
BMI-for-Age
Shape of Growth Curves: Weight-for-Stature versus
BMI-for-Age
10
15
20
25
30
35
24 72 120 168 216
Age (months)B
MI
0
5
10
15
20
25
30
35
80 90 100 110 120 130
Stature (cm)
Wei
gh
t (k
g)
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 Differs by 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 CutoffsBMI-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.
• 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
Can you see risk?
• This boy is 3 years, 3 weeks old.
• Is his BMI-for-age
- below the 5th percentile? - 5th to <85th percentile: normal? - >85th to <95th percentile: at risk for overweight? - >95th percentile: 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= >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
- below the 5th percentile? - 5th to <85th percentile: normal? - >85th to <95th percentile: at
risk for overweight? - >95th percentile: 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= 10th percentile Normal
BMI BMI
BMIBMI
Can you see risk?
• This girl is 4 years old.• Is her BMI-for-age
- below the 5th percentile?- 5th to <85th percentile: normal?- >85th to <95th percentile: at
risk for overweight?- >95th percentile: 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= 94thpercentile
At risk for
overweight
Plotted BMI-for-Age
Girls: 2 to 20 years
BMI
BMIBMI
BMI
5 1/2 year old boy
Weight: 41.5 lb
Height: 43 in
BMI= 15.8
BMI-for-age=50th %tile
Inaccurate height measurement: 42.25
BMI=16.3
BMI-for-age=75th %tile
Accurate Measurements are Critical
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
Available CDC Growth ChartsAvailable CDC Growth Charts
• Birth to 36 months
Weight-for-length
Length-for-age
Weight-for-age
Head circumference-for-age
• Birth to 36 months
Weight-for-length
Length-for-age
Weight-for-age
Head circumference-for-age
Available CDC Growth ChartsAvailable CDC Growth Charts
• 2 to 20 years
BMI-for-age
Stature-for-age
Weight-for-age
Weight-for-height
• 2 to 20 years
BMI-for-age
Stature-for-age
Weight-for-age
Weight-for-height
Steps to Plot BMI-for-AgeSteps to Plot BMI-for-Age
• Select appropriate growth chart• Record data• Obtain accurate weight and
height measurements• Calculate BMI• Plot measurements• Interpret plotted measurements
• Select appropriate growth chart• Record data• Obtain accurate weight and
height measurements• Calculate BMI• Plot measurements• Interpret plotted measurements
Case Study: “Sam” Case Study: “Sam”
• Name: Sam• Weight: 37 lb 4 oz (16.9 kg)• Height: 41.5 inches (105 cm)• DOB (date of birth): 9/15/1994• DOV (date of visit): 4/4/1998
• Name: Sam• Weight: 37 lb 4 oz (16.9 kg)• Height: 41.5 inches (105 cm)• DOB (date of birth): 9/15/1994• DOV (date of visit): 4/4/1998
Data Entry Table for BMI-for-AgeData Entry Table for BMI-for-Age
Mother’s Height________Father’s Height________
Age
4/4/98
GestationalAge________ Weeks
Weight
37 lb 4 oz
CommentDate Height BMI
41.5 in
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
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 SystemCalculating 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
Data Entry Table for BMI-for-AgeData Entry Table for BMI-for-Age
Mother’s Height________Father’s Height________
Age
3 1/24/4/98
GestationalAge________ Weeks
Weight
37 lb 4 oz
Comment
15.2
Date Height BMI
41.5 in
Sam’s BMI Plotted on Boy’s BMI-for-Age Chart
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
BMI-for-Age CutoffsBMI-for-Age Cutoffs
> 95th percentile Overweight
85th to < 95th Risk of overweight percentile
< 5th percentile Underweight
Interpreting the BMI-for-Age Chart 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
Future Directions for CDC Training
• Continuation of training at national meetings
• Development of a Web-based training module
• Training focus: accurate weighing and measuring, calculating BMI, plotting and interpreting the growth charts