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In dxf1david/cdcanthro: Calculate various z-scores, percentiles, etc. from the CDC growth charts

GENERATE SEX- AND AGE-STANDARDIZED WEIGHT, HEIGHT, AND BMI METRICS FROM THE CDC GROWTH CHARTS

Description

Generate z-scores, percentiles, and other metrics for weight, height, and BMI based on the 2000 CDC growth charts. Has a single function, 'anthro'. Requires the package data.table to be installed; library(cdcanthor) will also attach data.table.

The BMI metrics included z-scores and percentiles base on the growth charts, along with various newer metrics such as extended BMIz, percent of the 50th and 95th percentiles.

Usage

cdcanthro(data, age = age_in_months, wt = weight_kg, ht = height_cm, bmi = bmi)
# OR
# cdcanthro(data, age_in_months, weight_kg, height_cm, bmi)

# Do NOT put arguments in quotation marks

Arguments

data	data.frame or data.table
age	age in months specified as accuately as possible.
wt	weight (kg).
ht	height (cm).
bmi	BMI, kg/m^2.

Details

Expects sex to be coded as 1 (boys) or 2 (girls) in data. Weight is in kg, and ht is in cm. BMI is kg/m^2.

Age in months should be given as accurately as possible because the function linearly interpolates between ages. If completed number of months is known (e.g., NHANES), add 0.5.

If age is in days, divide by 30.4375 so that a child who is 3672 days old would have an age in months of 120.641.

For additional information on age, see information on agemos at https://www.cdc.gov/nccdphp/dnpao/growthcharts/resources/sas.htm

Value

Returns a data.table containing the original data and various weight, height, and BMI metrics. Can convert this to a dataframe with 'setDF(output_data)'.

Variables in output:

waz, haz, bmiz: CDC –for-age z-scores for Weight, Height, and BMI

mod_waz, mod_haz, mod_bmiz: modified z-scores

ext_bmip and ext_bmiz: extended BMI percentile and z-score

Note

Do NOT put arguments in quotation marks, such as cdcanthro(data,'age','wt','ht','bmi'). Use: cdcanthro(data, age, wt, ht, bmi)

Reference data are the merged LMS data files at https://www.cdc.gov/growthcharts/percentile_data_files.htm

Author(s)

David Freedman

References

Kuczmarski RJ, Ogden CL, Guo SS, Grummer-Strawn LM, Flegal KM, Mei Z, et al. 2000 CDC Growth Charts for the United States: methods and development. Vital and Health Statistics Series 11, Data from the National Health Survey 2002;11:1–190.

Wei R, Ogden CL, Parsons VL, Freedman DS, Hales CM. A method for calculating BMI z-scores and percentiles above the 95th percentile of the CDC growth charts. Annals of Human Biology 2020;47:514–21. https://doi.org/10.1080/03014460.2020.1808065.

Freedman DS, Woo JG, Ogden CL, Xu JH, Cole TJ. Distance and Percent Distance from Median BMI as Alternatives to BMI z-score. Br J Nutr 2019;124:1–8. https://doi.org/10.1017/S0007114519002046.

See Also

https://www.cdc.gov/nccdphp/dnpao/growthcharts/resources/sas.htm

Examples

data = expand.grid(sex=1:2, agem=120.5, wtk=c(30,60), htc=c(135,144));
data$bmi = data$wtk / (data$htc/100)^2;
data = cdcanthro(data, age=agem, wt=wtk, ht=htc, bmi);
# OR data = cdcanthro(data, agem, wtk, htc, bmi);
round(data,2)
# setDF(data) to convert to a dataframe

nhanes   # NHANES data (2015/16 and 2017/18)
nhanes  = nhanes[!is.na(bmi),] # exclude subjects with missing wt/ht
nhanes$agemos = nhanes$agemos + 0.5   # because agemos is completed number of months
data = cdcanthro(nhanes, age=agemos, wt, ht, bmi)
# OR data = cdcanthro(nhanes, agemos, wt, ht, bmi)
round(data, 2)

dxf1david/cdcanthro documentation built on April 22, 2022, 12:43 a.m.