What are the main differences in data structure between the continuous NHANES and NHANES III?
The continuous NHANES (1999-present) are conducted annually and released in two-year cycles, so the continuous NHANES is organized by survey cycles, namely, NHANES 1999-2000, 2001-2002, 2003-2004, etc. Each cycle is divided into four sections labeled by data collection method: Demographics, Examination, Laboratory, and Questionnaire. Within each section are many components – groups of related variables packaged in a data file according to topics. NHANES III was conducted in two phases, from 1988-91 and from 1992-94. However, the NHANES III data releases were not structured according to survey phases. Instead, they were organized according to the time of the data component release. Two specific releases contain the majority of data of interest to most researchers – these are Series 11, No. 1a and Series 11, No. 2a. Series 11 No. 1a contains the majority of the data and corresponding documentation for the survey interview and examination components.
