st: Generating a nested case-control study

["Cornelia Zekveld" <czekveld@hotmail.com>]

Dear statalisters,


I have an occupational cohort (n=866, cases=222) and would like to generate 
cases and controls from the data. I'd like to have as many controls as 
possible, with the two requirements:

1) The control must have been employed when the employee became a case (risk 
set sampling)
2) The control must have started employement around the same time as the 
case (up to 6 months before but not after).

It is also OK to use, as a control, someone who becomes a case at a later 
time.


I have come across the command -sttocc- but it only takes care of the first 
requirement.  I do not know how to incorporate the second constraint into 
the command.

Are there other stata commands that I'm not aware of that will be of help 
here?

Also, I want to know whether -sttocc- samples the controls with replacement?
It seems to be the case sine I have set the option number(#) to 30, just to 
see what happens and it was possible to generate 30 controls for each case - 
which seems odd given the cohort sample size.

Is it possible that a subject can be a control for more than one case?  Is 
there anything wrong with this?

Any help will be greatly appreciated!!

Thank you,
Cornelia

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