Cross-Sectional Studies

Abstract

In cohort studies, subjects are followed in a forward direction from exposure to outcome, and inferential reasoning is from cause to effect. In case-control studies, subjects are investigated in a backward direction from outcome to exposure; inference is from effect to cause. In cross-sectional studies, the exposure and outcome are both determined at the same point, or cross section, in time [1]. (Hence, another name for this design is prevalence study.) Cross-sectional studies share many of the features of case-control studies. They carry an additional disadvantage, however; since exposure is ascertained at the same point in time as the outcome, the investigator cannot be certain that exposure preceded outcome. As we shall see, this disadvantage has important implications for causal inference.