Incidence density sampling

[PRITI SINGH]

Hello,

I need to perform incidence density sampling using the following dataset. I have a dataset with patient information: example shown below. There are people who are hospitalized and acquire disease X after certain days of hospitalization.
I need to perform 1:3 matching for cases and control based on length of stay (LOS) and admission month. I need to include people who later got the disease but were disease free until certain time, as controls for other cases with same LOS. Thank you.

** Example generated by -dataex-. For more info, type help dataex
clear
input float(case LOS_total_days adm_month Person_visit_ID)
0 9.3 8 3
0 9.3 8 3
0 38.4 3 7
0 38.4 3 7
0 38.4 3 7
0 38.4 3 7
0 6.4 2 8
0 6.4 2 8
0 4.7 9 10
0 10.9 7 17
0 10.9 7 17
0 10.9 7 17
0 32 2 21
0 32 2 21

[Mike Lacy]

One thread that might be of use is at https://www.statalist.org/forums/for...age-and-gender

[PRITI SINGH]

Thank you, but how do I code controls for same or greater LOS

[Clyde Schechter]

Your example data is not usable for purpose because it contains no cases, only controls. Moreover, in order to achieve

I need to include people who later got the disease but were disease free until certain time, as controls for other cases with same LOS.

the data must include information about when those people who got disease X got it. Moreover, that additional information needs to be able to be compared to the dates corresponding to the observations of controls with whom they might match. That is, if information about the onset of disease X is available in some variable that provides the specific date, then the information about admission must also be specific dates, not just months.