A cross-sectional study, a type of descriptive, observational study, involves measuring different variables in the population of interest at a single point in time. This simultaneous data gathering is often thought of as a snapshot of conditions present at that instant. Its most important application lies in the field of epidemiology and disease research. Although it offers several advantages, such as the ease of assessing the prevalence of diseases, a cross-sectional study nevertheless has limitations.
Ease of Data Gathering and Assessment
The nature of cross-sectional studies offers a quick and easy way for an epidemiologist or any kind of researcher to quickly amass data. While some special case studies do require more specific data, for most cross-sectional studies, routinely collected data will suffice. This allows for quick and easy data gathering even for a large target population. Assessment of outcomes and risk factors for the entire population is also done with little trouble, as the sample is a near-perfect snapshot of the whole.
Low to Moderate Cost
The ease of gathering the needed information translates to cost-effectiveness. Many hospitals and census bureaus have that information already in hand, saving the researcher the trouble of gathering it, a time-consuming and expensive activity. The low cost involved in cross-sectional studies make it possible to conduct more thorough investigations of the population's overall condition.
The snapshot nature of cross-sectional studies, while convenient, does have its downside in that it doesn't provide a good basis for establishing causality. Two distinct variables are measured at the same point in time. Cross-sectional studies can say that the two are related somehow, but they cannot positively determine if one caused the other. Cross-sectional studies also fail on the part of confounding factors. Additional variables may affect the relationship between the variables of interest but not affect those variables themselves. Such observations are often lost in cross-sectional studies.
This limitation stems from the tools used for data gathering, either by the researcher himself or by hospital or census bureau employees. Tools such as pedometers, scales and sphygmomanometers are more or less accurate, but the most common tools used for data gathering, questionnaires, introduce a prevalence-incidence bias known as the Neyman bias. Even if the researcher uses a completely objective questionnaire, the person answering cannot answer questions involving past events with perfect accuracy. This either magnifies or minimizes the effects of certain variables, affecting the cross-sectional study's results.