Final answer:
Medical geography, often intersecting with social epidemiology, is the study examining the health changes in people migrating from one country to another, with Franz Boas's research emphasizing the role of various determinants of health.
Step-by-step explanation:
The type of study that examines changes in the health of people who move from one country to another is known as medical geography, which often overlaps with fields like social epidemiology and population health. This interdisciplinary study observes how migration, as a form of human mobility, impacts health outcomes by considering social and physical environmental factors that affect immigrants and emigrants. Notably, Franz Boas's research highlighted that health is shaped by an array of determinants, including many influenced by one's social and physical surroundings. With migration being a significant characteristic of human behavior, investigating the health implications brings valuable insights into global and local health trends as populations move and change their environment.