Translations:Advanced Field Epi:Manual 1 - Disease Investigation/263/en
In a cohort study animals that are free of the disease of interest are selected based on presence or absence of one or more defined risk factors (presence of the risk factor = exposed group and absence of the risk factor = unexposed group). The selected animals are then monitored forward in time to measure the occurrence of the disease of interest in each group. In some cases where detailed retrospective records are available it may be possible to use retrospective data to perform a cohort study but the approach is still the same.