Key Concepts about Merging and Appending NHANES Data for PAQ Analyses

In addition to combining variables from different files, a typical NHANES analytic dataset will include data from two or more NHANES cycles. You will need to merge data to combine variables from different data files collected during the same cycle and append data files to combine data from different years. Now that you’ve downloaded the necessary data from the 2003-2004 and 2005-2006 NHANES cycles you are ready to combine the DEMO and PAQ files using the merge and append functions. The resulting dataset will form the basis for your analytic dataset.


 When merging data, it is important to note the number of records per person in each of the data files you will be using.  The DEMO and PAQ files have one record per person. In contrast, the PAQIAF includes one or more records per study participant who indicated participation in leisure activities, as they detail the frequency and intensity of each leisure activity reported.