Possibly a very basic question, but I would really appreciate clarification from those with a strong background in stats/epi.
I have a number of human patient medical records. They are retrospective and longitudinal. Observation from 2000 to 2016 of 18 to 65 yr olds. However, some patients will not have a complete 16-year record as:
1) Their record will appear only when they turn 18, so I may only have records e.g., from 2008 for some patients.
2) A patient may die (but there won't be an indication) before 2016.
Each patient will have a number of events e.g., prescription of a drug. I would like to calculate the mean number of these events a patient will experience. However, with the patient records, not all being the same in duration I am unsure how I adjust the mean calculation.
As all ways, suggestions are very welcome.