in analytical epidemiology, a study where a population which is exposed to a presumed cause of disease is followed over a set period of time to monitor the appearance of the disease. A control group is also monitored to identify the cause and effect of infection. It is also known as a prospective study.
A study involving a group of people who either have or do not have a certain factor, such as exposure to a disease-causing agent. Such studies are usually used to compare disease rates.
A prospective investigation of the factors that might cause a disorder. A cohort (group) of persons who do not have the outcome of interest but who are exposed to the putative cause are compared to a cohort who are also free of the outcome but have not been exposed to the putative cause. Both cohorts are followed to compare the incidence of the outcome of interest. These studies are sometimes called prospective studies since the logic of the study design begins with exposure to the risk factor and the patients are followed for the development of the outcome. For example, a cohort of patients without evidence of liver disease but who have received a blood transfusion are compared to a cohort of patients without liver disease but have not been exposed to a blood transfusion. The two cohorts are followed over time and the incidence of hepatitis C is determined for each cohort.