How to treat patients without events in time-to-event analysis?
Generally, I would pick a value that is vastly outside the range of values that are non-imputed in this column since that'd probably cause more extreme (noticeable) errors in case they get included. So rather 9999 than -1. However, as you probably already attempted, the &quot;most correct&quot; solution would be to set it to NaN since the column is just not defined in these cases. If at any step during your analysis, some computation is done on the TimeSinceLastEvent column, anything but NaN would technically lead to incorrect results.
What is your downstream analysis strategy? Can you maybe split the data into two subsets (one with heart attacks, one without) and analyse them separately?