n this third type of observational study, asample of persons from a population is enrolled and theirexposures and health outcomes are measured simultaneously. Thecross-sectional study tends to assess the presence (prevalence) ofthe health outcome at that point of time without regard to duration.For example, in a cross-sectional study of diabetes, some of theenrollees with diabetes may have lived with their diabetes formany years, while others may have been recently diagnosed.