As compared to a routine case control study, Nested case control study avoids problems related to-
In Nested case control studies, the exposure has been either measured before the study itself or the samples have been collected, so that the findings cannot change due to any bias. Confounding bias is not reduced by Nested case control study. Since a nested case control study is pa of a coho study, it actually takes more time. Randomization is not involved in nested case control study. In a Nested case control study, interviews are performed at the beginning of the study (at baseline) and data are obtained before the disease has developed, thereby eliminating the problem of Recall bias.
Temporal association
Confounding bias
Need for long follow up
Randomization
Case Control Study, Combined Designs