See also “ Types of epidemiological studies” and “ Statistical analysis of data.” Explanatory research or causal inference: to establish causal mechanisms.Predictive research: to forecast outcomes (e.g., for prevention, diagnosis, or management).Descriptive research: to summarize characteristics of a group.Clinical epidemiology: the application of the principles of classical epidemiology to patients in a clinical setting.Classical epidemiology: the study of the determinants and distribution of disease in populations.See also “ Interpreting medical evidence,” “ Statistical analysis of data,” and “ Population health.” Fundamental concepts in epidemiology The following concepts are discussed separately: measures of disease frequency (e.g., incidence, prevalence, mortality rates), measures of association (e.g., relative risk, absolute risk reduction), measures used in the evaluation of diagnostic research studies (e.g., sensitivity, specificity), precision and validity, critical appraisal, the practice of evidence-based medicine, and foundational statistical concepts (e.g., measures of central tendency, measures of dispersion, normal distribution, confidence intervals). Other reasons for observed associations in epidemiological studies may include errors (e.g., random error, systematic errors), confounding, and reverse causality. An association between two variables (i.e., exposure and outcome) does not necessarily imply a causal relationship. Measures such as proportions, rates, and ratios can be calculated for the data collected. In experimental studies (e.g., randomized controlled trials), an intervention is performed to study its impact on a particular outcome. Analytical studies (e.g., cohort studies, case-control studies) seek to assess the association between exposures and outcomes. case series, ecological studies) characterize factors related to individuals with a particular outcome. The two main types of epidemiological studies are observational and experimental. Clinical epidemiology applies the principles of classical epidemiology to the prevention, detection, and treatment of disease in a clinical setting. What makes it 'retrospective' is that you are working from effect to cause, not vice-versa.Classical epidemiology is the study of the distribution and determinants of disease in populations. You can start collecting data, or you can do a chart review, or you can do a combination. All this means is that you are working from outcome to suspected cause. It is important to note here what is meant by 'retrospective'.

You can substitute any outcome of interest for Cases (Disease) versus Controls (No disease) (e.g., chronic high blood sugar versus not chronic high blood sugar), and.Remember that in the case-control schematic: Here is a simple schematic comparing Cohort and Case-control study: This is where rules (research design) come into play to keep us honest and prudent. It can be very exciting to think that we may have noticed something that no one else has noticed. You begin to backtrack to try to find the source or common element of the infection. There are others from the same area that are not infected. You have patients that are sick with a new disease. for rare disease, large sample sizes or long follow-up necessary.Ĭase-control studies are retrospective in nature.exposure may be linked to a hidden confounder.administratively easier and cheaper than RCT.eligibility criteria and outcome assessments can be standardised.can establish timing and directionality of events.You can substitute Treated versus Not treated for Exposed versus Not exposed.You can substitute any outcome of interest for Disease versus No disease (e.g., chronic high blood sugar versus not chronic high blood sugar), and.It can be a concurrent study, meaning that you start collecting data now non-current, typical of a chart review or review of other records, or a combination of the two. It is important to note that what makes the Cohort design 'prospective' in nature is that you are working from suspected cause to effect (or outcome). Here is a simple schematic of the Cohort study: As always, it can be exciting to think that you may have noticed something that no one else has noticed, and you want to proceed according to certain rules to insure that you remain honest and prudent. So you set out to examine some representative cases very closely to see if you are correct. Treatment with a particular procedure or medication seems to lead to a resolution of particular symptoms.seems to lead to a particular disease state, or Exposure to a particular chemical, water from a particular source, etc.Cohort studies are prospective in nature.

Retrospective cohort vs case control