Task 1: Key Concepts About How Dietary Data Fit Into the NHANES
Data
Structure
Cycles
The Continuous NHANES data are released in two-year cycles beginning with
NHANES 1999-2000 (See the "Overview of NHANES Survey Design and Weights" module for
information about the reasons for this policy.) Some survey topics areas are
included in all survey cycles, whereas others are included in selected cycles.
Sections
The data for each survey cycle are composed of five sections: Demographics,
Dietary, Examination, Laboratory, and Questionnaire.
- Demographics files contain survey design variables such as
weights, strata and primary sampling units, as well as demographic
characteristics, such as sex, age, and race.
- Dietary files contain information collected on the diet of participants. These files include data from the dietary recall data, food frequency and dietary supplements questionnaires, as well as a number of diet related questions that follow the dietary recall in the Mobile Examination Center.
- Examination files contain information collected through
physical exams (including anthropometric and physical activity data), and dental
exams.
- Laboratory files contain results from analyses of blood,
urine, hair, tuberculin skin test, air, and household dust and water specimens.
These files also include serum nutrient and cholesterol values, which can be
used for nutritional assessment.
- Questionnaire files contain data collected through household and MEC interviews and mailed questionnaires.
Each section contains groups of related variables, packaged
in one or more data files for each 2-year cycle. This organization scheme
allows for efficiency in posting data to the website, downloading them, and
analyzing them.
For each cycle of the continuous NHANES, the 1999-2010 Survey Content Brochure provides:
- data files associated
with each section,
- age ranges for which data
on specific variables were collected, and
- notes describing any additional (non-age-based)
exclusions.
The following table lists examples of the diet-related
survey data files and topics that were included in NHANES 2003-2004.
Diet-Related Survey Components in NHANES 2003-2004
| Section |
Data Topics |
Data Collection Setting |
| Examination |
-
Dietary recalls (4 data files)
-
Body composition
-
Body measurements
-
Blood pressure examination
-
Physical activity monitor
-
Cardiovascular fitness
|
- Mobile Examination Center (MEC) (first dietary recall)
- Telephone follow-up (second dietary recall)
|
| Laboratory |
- Serum cholesterol and lipoproteins
- Serum and red blood cell folate
- Iron status and hematology
- Other nutritional biochemistry data
|
|