Which among the following is the major practical problem in a coho study?: (A) Differential loss of follow up, (B) Long duration of study, (C) Can be used only for rare conditions, (D) None of the above
Answer is A. Disadvantages of coho studies: Have to follow large numbers of subjects for a long time. They can be very expensive and time consuming. They are not good for rare diseases. They are not good for diseases with a long latency. Differential loss to follow up can introduce bias.