Unlike the case control studies the case base studies are well suited to the cross sectional extractions from the reimbursement data bases that we usually do.
The case base studies use the whole population of the database as a control group , including the subjects who are affected by the disease (ie the cases).
Thus, making no difference whether the subjects have the disease or not , the control group is far more easy to constitute.
Citation: Chui TT-T, Lee W-C (2013) A Regression-Based Method for Estimating Risks and Relative Risks in Case-Base Studies. PLoS ONE 8(12): e83275. doi:10.1371/journal.pone.0083275