3.7 Longitudinal Data

3.7.1 Long Format

If data is repeatedly collected on patients, each observation or assessment can be in a separate row. This makes data checking and cleaning simpler, and reduces the size of your data dictionary because there are fewer variables.

Example of data in long format. There is one entry for each observation

Static variables, like sex and age, or variables that were collected at a single time point can be entered in a separate sheet.

3.7.2 Wide Format

If data are entered in wide format, with one row per patient then the variable names should be consistent across the time points, as shown below.

⚠️ All variable names must be unique!

Example of data in wide format. Each person is in a row and each assessment has a group of columns