Observational Studies in Veterinary Research and Practice

One of the most important applications of epidemiology is the investigation of the causes of diseases. In this regard, the appropriate design of study to approach the causes and risk factors of a disease is vital. Observational studies are a category of studies that help the researcher in identifying risk factors for disease occurrence and quantifying the effect of these factors on it, thereby influencing its control within the population. These studies are conducted through observing the natural behavior of disease in the population. Accurate and precise data collection (a part that receives less attention in the country) forms the cornerstone of these studies, requiring special attention from educational, extension, and research centers. In this article, various types of observational studies are initially introduced in general terms. Subsequently, cross-sectional, case-control, and cohort studies, as the three main types of observational studies, are comprehensively explained. The methods of grouping for study entry, calculation of minimum sample size, applications, and advantages and disadvantages of each study are described in detail. Additionally, the capabilities that each type of these studies provides to the researcher for interpreting the causality of the occurrence or the desired outcome in the study are provided at the end of each section. After introducing the implementation method of each study, depending on the case, references to three or four articles with similar study designs are provided to serve as examples of observational studies as a model. It should be noted that these types of studies are foundational for conducting intervention studies, and creating infrastructure for data recording and analysis is necessary for conducting these studies.