Understanding Cohort Studies in Research

Cohort Study

Observational study tracking exposed vs unexposed groups.

Case-Control Study

Comparative study of cases vs controls retrospectively.

Relative Risk (RR)

Ratio of risk in exposed vs unexposed groups.

Absolute Risk (AR)

Probability of an outcome occurring in a group.

Hazard Ratio (HR)

Risk comparison during a specific study time frame.

ARR (Absolute Risk Reduction)

Difference in risk between two groups.

ARI (Absolute Risk Increase)

Increase in risk due to exposure.

NNT (Number Needed to Treat)

Number of patients needed to treat for one benefit.

NNH (Number Needed to Harm)

Number of patients needed to treat for one harm.

Endpoints

Outcomes measured in a study to assess effectiveness.

Statistical Significance

Likelihood that results are not due to chance.

Clinical Significance

Practical importance of study results in real-world settings.

95% Confidence Interval (CI)

Range of values likely to contain the true effect.

Prospective Study

Study design following participants forward in time.

Retrospective Study

Study design looking back at past data.

Strengths of Cohort Studies

Good for studying rare exposures and long-term effects.

Weaknesses of Cohort Studies

Time-consuming and expensive; potential for loss to follow-up.

Strengths of Case-Control Studies

Efficient for studying rare outcomes and quicker results.

Weaknesses of Case-Control Studies

Recall bias and difficulty establishing temporal relationships.

Incidence Calculation

Determining new cases in a defined population over time.

Risk Factor (RF)

Characteristic that increases the likelihood of an outcome.

Follow-Up Time

Duration participants are monitored in a study.

Cohort Identification

Groups defined by exposure status at study start.