<prompt> Migration study is used to studySociodemographic reasons for migration of a populationPrevalence of disease in a populationEnvironmental and genetic factors in a disease in populationDiseases with long incubation period  <response>: Large-scale migration of human populations from one country to another provides a unique oppounity to evaluate the role of the possible genetic and environmental factors in the occurrence of disease in a population.Migration studies can be carried out in 2 ways -a Comparision of disease and death rates for migrants with that kin who have stayed at home. Genetically similar groups living in different environmental conditionsb Comparision of migrants with the local population of the host country. genetically different groups living in the same environmentPark 23e pg: 67 