The contents of the SASHELP library to an extent depend on which modules are licensed and installed. Not all but many of the modules will add data sets for specific examples.
If you are looking for example data to use with specific procedures I would recommend looking in your online SAS help under Learning to Use SAS in the Sample SAS Programs for the SAS module and procedure. There are likely to me one or more sets available.
In one sense, most of the data sets with DATE or YEAR variables have chance of being "longitudinal data" but not a lot of health data is represented in the basic SASHELP examples.