R/iotf.R

In statist7/sitar: Super Imposition by Translation and Rotation Growth Curve Analysis

#' IOTF international body mass index reference
#'
#' The IOTF (International Obesity TaskForce) BMI growth reference
#' (Cole and Lobstein 2012), fitted by the LMS method and summarised by values
#' of L, M and S by sex and postnatal age from 2 to 18 years.
#'
#' The IOTF cutoffs for overweight and obesity (and also thinness) (see
#' Cole et al 2000, 2007) can be obtained from this BMI reference.
#' See the example for how to convert between cutoffs and z-scores.
#'
#' The L, M and S values for each measurement correspond respectively to the
#' Box-Cox power, median and coefficient of variation of the distribution by
#' age and sex (Cole & Green 1992). The measurement short name and units
#' for \code{\link{LMS2z}} are bmi (kg/m2).
#'
#' @name iotf
#' @docType data
#' @format A tibble with 66 observations on the following 5 variables:
#' \describe{
#' \item{years}{numeric vector - postnatal age in years}
#' \item{L.bmi}{numeric vector}
#' \item{M.bmi}{numeric vector}
#' \item{S.bmi}{numeric vector}
#' \item{sex}{two-level factor with level 1 male and level 2 female} }
#' @references Cole TJ, Green PJ. Smoothing reference centile curves: the LMS
#' method and penalized likelihood. Stat Med 1992;11:1305-19.
#'
#' Cole TJ, Bellizzi MC, Flegal KM, Dietz WH. Establishing a standard
#' definition for child overweight and obesity worldwide: international survey.
#' BMJ 2000;320:1240-3.
#'
#' Cole TJ, Flegal KM, Nicholls D, Jackson AA. Body mass index cut offs to
#' define thinness in children and adolescents: international survey.
#' BMJ 2007;335:194-7.
#'
#' Cole TJ, Lobstein T. Extended international (IOTF) body mass index cut-offs
#' for thinness, overweight and obesity. Ped Obes 2012;7:284-94.

#' @source The values are tabulated in the Excel spreadsheet IOTF_LMS.xls
#' provided with the Excel add-in LMSgrowth from
#' https://www.healthforallchildren.com/shop-base/software/lmsgrowth/
#' @keywords datasets
#' @examples
#' data(iotf)
#' ## calculate z-scores by sex corresponding to IOTF cutoffs for thinness,
#' ## overweight and obesity
#' co <- data.frame(cutoff = c(16, 17, 18.5, 25, 30),
#'   grade = c('thinness 3', 'thinness 2', 'thinness 1',
#'     'overweight', 'obesity'))
#' sexes <- c('boys', 'girls')
#' with(co,
#'   cbind(co, lapply(setNames(sexes, sexes), function(x)
#'     LMS2z(x = 18, y = cutoff, sex = x,
#'           measure = 'bmi', ref = 'iotf'))))
"iotf"