This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
Migration study is used to study: 
Select and explain. 
A. Sociodemographic reasons for migration of a population, B. Prevelence of disease in a population, C. Environment and genetic factors in a disease in population, D. Disease with Long incubation period
C: Environment and genetic factors in a disease in population
Answer: C: Environment and genetic factors in a disease in population 
Explanation: MIGRATION STUDIES Use: Evaluation of role of possible Genetic and Environmental factors in occurence of a disease in a population. Study Design: Comparision of Disease rates & Death rates of, Migrants with kin who stayed at home. MIgrants with Local population of host country. Limitation: Non-random assignment to Groups: Migrants are self-selected Environmental factors may act at ceain age/point only Not useful for disease with long incubation period Ref: Park 25th edition Pgno: 75