*Geek Box: Cross-Sectional Study
A cross sectional study is a type of observational study design, where data is analysed from a sample population at a specific moment in time [i.e., a ‘cross-section’ of a group]. The researchers are interested in looking at a particular exposure and outcome and investigating whether the prevalence of the outcome differs based on levels a particular exposure.
For example, does the prevalence of type-2 diabetes differ between levels of dietary fat intake? In effect, a cross-sectional study is a snapshot in time, evaluating the relationship between the exposure [in this study, levels of social jetlag] and outcome [MetSx T2D, and risk factors].
Cross-sectional studies can be very useful to look at specific characteristics of a population with a relevant exposure, and compare with healthy or non-exposed populations, to identify differences. In a cross-sectional study, results are presented as ‘prevalence ratios’ [PR], which are used in cross-sectional studies and analogous to risk ratios in a prospective study. They are prone to certain biases, for example recall bias, or selection bias. However, they are useful for identifying prevalence of an exposure and outcome in a population.