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Simple linear regression for public health: About the NHANES data

Our data comes from the National Health and Nutrition Examination Survey (NHANES), run by the CDC in the US. This data describes the demographics, physical properties, health and lifestyle of children and adults. Every year 5,000 participants are enrolled and the data is used for research and policy-making purposes. We are using data from the 2009-2010 and 2011-2012 editions of this survey. You can find out more about NHANES on the CDC website here.

In the original data, particular subsets of the population are oversampled, such that conclusions based on the data are also representative of ethnic minorities. This introduces complications into the analysis. Therefore, we are using a subset of the data that can be treated as a simple random sample of the US population. This subset is suitable for educational purposes, but may not be useful for research applications. The subsetting is done by the load_data.R script, which you can find here and inside the scripts folder of the workshop_project workshop directory.

The variable names and the associated descriptions can be found in the table below.

Variable Definition
ID A unique sample identifier.
Sex Sex of study participant coded as male or female.
Age Age in years at screening of study participant. Note: Subjects 80 years or older were recorded as 80.
AgeMonths Age in months.
Work Indicates whether the individual is current working or not. One of Looking, NotWorking or Working.
Weight Weight in kg.
Height Standing height in cm. Reported for participants aged 2 years or older.
BMI Body mass index (weight/height2 in kg/m2). Reported for participants aged 2 years or older.
Pulse 60 second pulse rate.
BPSysAve Combined systolic blood pressure reading, following the procedure outlined for BPXSAR.
BPDiaAve Combined diastolic blood pressure reading, following the procedure outlined for BPXDAR.
TotChol Total HDL cholesterol in mmol/L. Reported for participants aged 6 years or older.
UrineFlow1 Urine flow rate (urine volume/time since last urination) in mL/min - first test. Reported for participants aged 6 years or older.
Depressed Self-reported number of days where participant felt down, depressed or hopeless. Reported for participants aged 18 years or older. One of None, Several, Majority (more than half the days), or AlmostAll.
PhysActive Participant does moderate or vigorous-intensity sports, fitness or recreational activities (Yes or No). Reported for participants 12 years or older.
SmokeNow Study participant currently smokes cigarettes regularly. Reported for participants aged 20 years or older as Yes or No, provieded they answered Yes to having somked 100 or more cigarettes in their life time. All subjects who have not smoked 100 or more cigarettes are listed as NA here.
FEV1 Baseline 1st Test Spirometry, Forced Expiratory Volume in the first 1.0 second, in mL.
Hemoglobin Complete Blood Count with 5-part Differential - Whole Blood (CBC_F)