Analytical epidemiological study is a more detailed and all-encompassing epidemiological study than the descriptive epidemiological study. An analytical study describes the association between exposure and outcome (disease).
It is meant to test the hypothesis of a descriptive epidemiology. Analytical study investigates the cause of a disease by studying how exposure of individuals relate to the disease (i.e. it studies the relationship between a disease and its determinants).
Virtually all epidemiological studies (except observational studies) are analytical in nature. In analytical epidemiological study, the epidemiologists or researcher systematically investigates whether or not the risk of a disease is different for exposed and unexposed persons in relation to a particular variable. Analytical epidemiological studies deal more with the “how” of a disease/infection in a population at a given time.
It looks at the cause of a disease, the process of transmission (i.e. the how), and the relationship of the different factors or variables of the disease (i.e. the why) in a population/community. This study usually involves some series of laboratory procedures in order to supplement epidemiological studies.
Analytical epidemiological study may include:
Case control studies
Case control study is defined as an epidemiological study in which two existing groups differing in the outcome of a particular disease are identified and compared on the basis of some supposed causal attribute. In case control studies, two groups of people (the case and the control) are compared. The case is the group of people with the disease or health condition under study while the control is the similar group of people who do not have the disease or health condition under study.
Case-control studies are observational epidemiological studies and are unique in their data gathering patterns in regards to the outbreak of an infectious disease in a defined human or animal population. Whereas the cohort study is concerned with frequency of disease in exposed and non-exposed individuals, the case-control study is concerned with the frequency and amount of exposure in subjects with a specific disease (cases) and people without the disease (controls).
Cohort (prospective) studies
Cohort (prospective) studies are epidemiological studies that follow over time groups of individuals who are alike in many ways but differ by a certain characteristic (for example, male doctors who drink alcohol and those who do not drink alcohol) and compare them for a particular outcome of a disease condition (such as obesity or diabetes). It is a longitudinal cohort study that follows over time a group of similar individuals who differ with respect to certain factors under study, to determine how these factors affect rates of a certain outcome.
The distinguishing feature of a prospective cohort study is that at the time that the investigators or researchers begin enrolling subjects and collecting baseline exposure information about that particular disease or health condition under study, none of the subjects (under investigation) has developed any of the disease outcomes of interest.
Cohort studies can be classified as prospective or retrospective based on when outcomes occurred in relation to the enrollment of the cohort. For a retrospective cohort study, the investigators or researchers (go back in time to) conceive the study and begin identifying and enrolling subjects after outcomes have already occurred.
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