Confounding and bias is more a problem in prospective cohort studies than retrospective cohort studies.

This statement is not entirely accurate. Both prospective and retrospective cohort studies are susceptible to confounding and bias, but the types and degrees of these issues can vary.

1. Prospective Cohort Studies: In these studies, researchers follow a group of people over time. The researchers collect data as events unfold, which can lead to more accurate and complete data. However, these studies can be affected by "selection bias" where the study population does not accurately represent the target population. Also, "observation bias" can occur when researchers' expectations affect the outcome of the study.

2. Retrospective Cohort Studies: These studies use existing data records to identify exposure and outcome. While they are quicker and less expensive than prospective studies, they are more susceptible to certain types