Retrospective observational cohort study
A retrospective observational cohort study is a specific type of epidemiological study that has the following characteristics:
🔍 Study Type:
Observational (non-interventional)
The researchers do not assign exposures or treatments; they simply observe what has already occurred.
📅 Time Orientation:
Both exposure and outcome have already occurred when the study begins.
Researchers look backward in time, using existing data, like medical records, databases, or patient charts.
👥 Design: Cohort
The study involves a defined group (cohort) of individuals who are classified based on exposure status (e.g., exposed vs. unexposed).
The outcomes of these groups are compared to determine if the exposure is associated with a specific outcome.
✅ Key Features: Based on existing records or databases.
No randomization or control over variables.
Useful for studying long-term effects or rare exposures.
Lower cost and faster than prospective studies.
Can be vulnerable to bias (e.g., selection bias, recall bias, missing data).
🧠 Example: A hospital wants to examine whether patients who took Drug A between 2010 and 2015 had a higher incidence of stroke than those who did not. Researchers use medical records to identify exposure and outcome retrospectively.
If you're using this for writing or classifying your study in a publication, you might phrase it like this:
“We conducted a retrospective observational cohort study to evaluate the association between [exposure] and [outcome] in patients treated at [location] between [years].”