Immortal time bias occurs when exposure time is misclassified in cohort studies; which description best fits it?

• A. Misclassification of exposure time in cohort studies where individuals must survive a period to be classified as exposed, artificially inflating survival time.
• B. A bias from recalling past exposures.
• C. A bias due to selection of only healthy participants.
• D. A bias introduced by loss to follow-up.

Answer: (C)