Cross-sectional surveys

Cross-sectional surveys may be descriptive e.g. assessing the prevalence of asthma in young children. They may be analytical e.g. investigating the association between a putative risk factor and a health outcome. This type of study is limited in its ability to draw valid conclusions as to the association between risk factor and health outcome. Since exposure and disease are assessed at the same point in time, cross-sectional surveys cannot always distinguish whether the exposure preceded the development of the disease or whether presence of the disease affected the individual’s level of exposure.

For factors that remain unaltered over time, such as sex, race, or blood group, cross-sectional surveys can provide evidence of a valid statistical association. However such instances are rare, and for the vast majority of associations evaluated, the temporal relationship between exposure and disease cannot be clearly determined. Therefore cross-sectional studies are useful for raising the question of the presence of an association rather than the testing of a hypothesis.