Time-Consuming and Expensive: Cohort studies, especially prospective ones, can take a long time to complete and require significant resources. Loss to Follow-Up: Participants may drop out over time, leading to potential bias if the loss is related to the exposure or outcome. Not Suitable for Rare Diseases: For diseases with low incidence, extremely large cohorts are required, making the study impractical. Exposure Misclassification: Inaccuracies in measuring exposure can lead to misclassification and affect the study's validity.
