|
We have been providing funds to the National Center for Health Statistics (NCHS)
to support modules in the National Health and Nutrition Examination Survey (NHANES) that are
critical to our risk factor monitoring mission. We collaborated on developing and fielding
a pilot test of a food frequency questionnaire (FFQ) and a wearable physical activity
monitor. Based on the success of these pilot tests, we incorporated the FFQ and physical
activity monitors in the full NHANES starting in 2003.
The NHANES has always included a single 24-hour dietary recall on each respondent to
link with socio-demographic and health data. Such data are useful for estimating mean
intakes of a population, but cannot alone provide estimates of usual intakes
of individuals or usual intake distributions
for the population because intra-individual variation in dietary intakes is quite large.
This means that prevalences of intakes above or below a particular recommended level
cannot be determined appropriately.
Adding an FFQ to the NHANES provides a remedy to this problem and allow estimates of
usual dietary intakes at both the individual and population levels. Individual-level
estimates can then be linked with health data, and the population-level estimates will
allow appropriate determination of the proportion of the population above/below a
recommended dietary level.
The NHANES has traditionally relied upon self-report to assess physical activity. Given
the potential for biased reporting, including physical activity monitors provides a
much-needed objective assessment of this emerging cancer risk factor (see Physical Activity).
Assessing physical activity with monitors is particularly valuable for studying
children, for whom self- or proxy-reports are unreliable.
|
