# NHANES

The National Health and Nutrition Examination Survey (NHANES) is conducted continuously in the United States. The studies started in the mid-20th century and originally targeted specific groups (adults, children, Hispanics, etc.). NHANES III was the last study using that strategy. Beginning in 1999 the data were gathered continuously and released in two year cycles. Since the objective is to obtain an overall health picture of the US civilian population, the extensive data only contain a few measures of body size and shape. These include stature, mass, BMI, and waist circumference.NHANES uses a sampling strategy in which the “tails” of distributions are oversampled. For example, underrepresented groups are included at a disproportionately high rate. This ensures that they are well-modeled in the data. As a result, each individual in the sample has an associated “sampling weight” indicative of the number of individuals in the general population they represent. Thus the sum of the sampling weights is the total number of individuals in the US Civilian population. **As a result, any statistical analysis of the NHANES data requires that the sampling weights be considered.** The official data analysis guidelines are published here.

The data are generally aggregated across at least four years. The 2011-2012 and 2013-2014 samples were the first to include a specific oversampling of Asians. As a result, the 2011-2014 data do a good job of modeling the primary racial/ethnic groups in the US: Whites, Blacks, Hispanics, and Asians. You can read more about the sampling strategy here.

The data made available for download here are those that will likely be of use for design considering body size and shape. Elements of the Demographics and Examination files have been combined (by person) so that all of the information is in one place.

### Variable Descriptions

RIAGENDR – gender (1=males, 2=females)

RIDRETH3 – race/ethnicity (1=Mexican American, 2=Other Hispanic, 3=Non-Hispanic White, 4=Non-Hispanic Black, 5=not used, 6=Non-Hispanic Asian, 7=Other Race)

RIDAGEYR – age in years

BMXHT – stature in mm (originally recorded in cm, but we use mm site-wide)

BMXBMI – body mass index, BMI (a measure of weight-for-stature)

BMXWT – mass in kg

BMXWAIST – waist circumference in mm (originally recorded in cm, but we use mm site-wide)

RIDEXPRG – pregnancy status at exam (1=yes, positive lab test or self-reported pregnant; 2=not pregnant; 3=unsure)

WTMEC2YR – full sample 2-year mobile examination center (MEC) exam weight (the sampling weight)

combinedWeight – calculated by us; this is the weight for a combined, 4-year sample

## Explore the Data

### Data Explorer

A tool for exploring the distributions of many of the most commonly used measures.

### Data Explorer Lite

A simplified tool for exploring stature, mass, and BMI.

## Downloads

### NHANES 2011-2014 Adult Data

We have parsed the data into CSV files. Adults are defined as 20 years and up (per typical NHANES analysis practice). The rows are individuals in the sample. The columns are the measures. The units are millimeters, except for weight, which is kg. Pregnant women are in the original data but excluded here. Variable names and code equivalents are detailed above. Remember you must use the statistical weights when analyzing these data.

### Summary Report 2011-2014

A Summary Report of the anthropometric data (stature, mass, and BMI) in the NHANES 2011-2014 sample. The analysis is broken down by age (children and adults as well as 2-year segments of adults), gender, and race/ethnicity. Measurements are provided in both inches and cm. The data available for download here will produce similar results when analyzed properly. [46 pages, 2.8MB]

*Fryar, C.D., Gu, Q., Ogden, C.L., Flegal, K.M., 2016, “Anthropometric reference data for children and adults: United States, 2011–2014”, National Center for Health Statistics. Vital Health Stat 3(39).*

### NHANES 2013-2016 Adult Data

These are the most recent data, but there are no published tables against which to compare your calculations (like there are with 2011-2014). We have parsed the data into CSV files. Adults are defined as 20 years and up (per typical NHANES analysis practice). The rows are individuals in the sample. The columns are the measures. The units are millimeters, except for weight, which is kg. Pregnant women are in the original data but excluded here. Variable names and code equivalents are detailed above. Remember you must use the statistical weights when analyzing these data.

male data (<1MB)female data (<1MB)