Basic Epidemiology Study Designs in Epidemiologic Research Thomas Songer, PhD Modified by Supercourse team * Descriptive study designs include case reports, case series, incidence studies, and ecologic studies. Epidemiological study designs, sources of systematic and random error (bias), and guidelines for assessing the causality of associations are discussed in section 5.1. A systematic review. There is no restriction on when the exposure information is collected or whether it relates to current and/or historical exposures. The latter may have been measured at the time of data collection [e.g. Nonetheless, this 4-fold classification of study types has several advantages over other classification schemes. The purpose of this article is to provide a brief overview of the range of study designs used to address research questions in clinical epidemiology. Descriptive studies are used to describe exposure and disease in a population, and can be used to generate hypotheses, but they are not designed to test hypotheses. Published by Oxford University Press on behalf of the International Epidemiological Association © The Author 2012; all rights reserved. non-hypertensive, mild hypertension, moderate hypertension and severe hypertension) or may be represented by a continuous measurement (e.g. First, it captures the important distinction between incidence and prevalence studies; in doing so it clarifies the distinctive feature of cross-sectional (prevalence) studies, namely that they involve prevalence data rather than incidence data. Such a study would on an average achieve the same findings as the full cohort study (Table 2), but would be considerably more efficient, since it would involve ascertaining the exposure histories of 5530 people (2765 cases and 2765 controls) rather than 20 000 people. However, they are often very expensive in terms of time and resources, and the equivalent results may be achieved more efficiently by using an incidence case–control study design. Prevalence studies are a subgroup of cross-sectional studies in which the disease outcome is dichotomous. 42 Terms. Table 4 shows data from a prevalence study of 20 000 people (this example has been designed to correspond to the incidence study examples given above, assuming that the exposure has no effect on disease duration and that there is no immigration into or emigration from the prevalence pool, so that no one leaves the pool except by disease onset, death or recovery7). Findings from a hypothetical prevalence case–control study based on the population represented in Table 3. the ‘survivors’ (those who did not develop the outcome at any time during the follow-up period). whether an exposure increases disease incidence) in prevalence studies. Nevertheless, for many common diseases, studying prevalence is often the only practical option and may be an important first step in the research process; furthermore, prevalence may be of interest in itself, e.g. all workers at a particular factory or all persons living in a particular geographical area) and incidence studies involving sampling on the basis of exposure, since the latter procedure merely redefines the study population (cohort).4, Findings from a hypothetical cohort study of 20 000 persons followed for 10 years. In many prevalence studies, information on exposure will be physically collected by the investigator and at the same time information on disease prevalence is collected. Outcome. having or not having hypertension). óÀ._ÓY²LW/Ü°Õé|ÀNI¡ë¸jW÷¸¨ÊˆÈ5¨(tBÐh„¶ÙÀïc—Š¬%=kEi4Ÿ)ö^ÄÆ0J²,ÍæÅw:;6YË!W!ógÃƓëVVj„õ¾ ¥wiQHÍi'A…‘ÀNVe9”›«/Ì.6U£²:#0Ø *K«Ü¶ >-•ZçiR¬h‰Ó)GÅÖ. Epidemiologic study designs In previous topics we investigated issues in defining disease and other health-related outcomes, in quantitating disease occurrence in populations, in relating disease rates to factors of interest, and in exploring and monitoring disease rates and relationships in populations. blood pressure). Cross … The method of calculation of the OR is the same as for any other case–control study, but special formulas must be used to compute confidence intervals and P-values.15, The third approach is to select controls longitudinally throughout the course of the study, an approach now usually referred to as ‘density sampling’7 (or concurrent sampling11); the resulting OR will estimate the rate ratio in the source population (which is 2.00 in Table 3). Research Assistant Professor of Epidemiology, Board Certified or Board Eligible AP/CP Full-Time or Part-Time Pathologist, Chief of ID, VA Ann Arbor Healthcare System, From source population (case–cohort sampling), Copyright © 2020 International Epidemiological Association. View this table: View inline; View popup; Table 1 . A RCT provides the best type of epidemiological study from which to draw conclusions on causality. However, the extension to continuous outcome measures does require further discussion. The study designs can be broadly classified as experimental or observational based on the approach used to assess whether exposure and an outcome are associated. Incidence studies are a subgroup of longitudinal study in which the outcome measure is dichotomous. current levels of airborne asbestos exposure, body mass index (BMI)] or at a previous time (e.g. Once this distinction has been drawn, then the different epidemiological study designs differ primarily in the manner in which information is drawn from the source population and risk … Risk Assessment A number of epidemiological research designs are used to evaluate the association between a disease and a suspected risk factor. Care transitions in the first 6 months following traumatic brain injury: Lessons from the CENTER-TBI study. Since these measurements are taken at a particular point in time, such studies are often referred to as ‘cross-sectional studies’. In epidemiology, the study mainly deals only with the distribution of diseases/conditions in humans and with the factors influencing the distribution and the frequency of diseases. Types of Epidemiological Studies Descriptive Studies Also termed as Cross-sectional studies they determine the disease frequency or prevalence of a condition. the incidence of being diagnosed with hypertension), or the prevalence of the disease state (e.g. Epidemiologists must have a sound understanding of the principles of study design. Field epidemiology and COVID-19: always more lessons to be learned, Commentary: Descent from the aerial palace, Development of a common scale for measuring healthy ageing across the world: results from the ATHLOS consortium, Evidence for familial clustering in breast cancer age of onset, Cohort profile: HABITAT—a longitudinal multilevel study of physical activity, sedentary behaviour and health and functioning in mid-to-late adulthood, About International Journal of Epidemiology, About the International Epidemiological Association, Extension to continuous exposures or outcomes, Receive exclusive offers and updates from Oxford Academic, Cohort Profile: The Helsinki Businessmen Study (HBS), Commentary: Multistage carcinogenesis and epidemiological studies of Types of Epidemiological Studies The study of disease distributions in the populations and the factors that influence this distribution is called as Epidemiology. In this course, you will learn about the main epidemiological study designs, including cross-sectional and ecological studies, case-control and cohort studies, as well as the more complex nested case-control and case-cohort designs. Most case–control studies involve density sampling (often with matching on a time variable such as calendar time or age), and therefore estimate the incidence rate ratio without the need for any rare disease assumption.16, Incidence studies are usually the preferred approach to studying the causes of disease, but they often involve lengthy periods of follow-up and large resources.17 Also, for some diseases (e.g. Epidemiological literature, studies are often referred to as ‘ cross-sectional studies provide a snapshot of a.! Occurrence all involve the same numerator: the number of epidemiological research designs are used to evaluate association. The incidence of being diagnosed with hypertension ), incidence may be useful for different purposes, as as. 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