My flippant answer: "No one is ever assigned Patient ID 0" It's mostly about expectations. Users of statistical software, who may or may not be programmers by

My flippant answer: "No one is ever assigned Patient ID 0" It's mostly about expectations. Users of statistical software, who may or may not be programmers by inclination, use 1-based indexing. The program they came from uses 1-based indexing (R, SAS, Stata, etc.). When you talk about data, you rarely talk about the 0th observation. It's just a recipe for errors to have to code switch between 0 and 1-based indexing.