Social epidemiology is the study of the causes and distribution of diseases. Social epidemiology can reveal how social problems are connected to the health of different populations. These epidemiological studies show that the health problems of high-income nations differ greatly from those of low-income nations. Some diseases, like cancer, are universal. But others, like obesity, heart disease, respiratory disease, and diabetes are much more common in high-income countries and are a direct result of a sedentary lifestyle combined with poor diet. High-income nations also have a higher incidence of depression (Bromet et al. 2011). In contrast, low-income nations suffer significantly from malaria and tuberculosis.
How does health differ around the world? Some theorists differentiate among three types of countries: core nations, semi-peripheral nations, and peripheral nations. Core nations are those that we think of as highly developed or industrialized, semi-peripheral nations are those that are often called developing or newly industrialized, and peripheral nations are those that are relatively undeveloped. While the most pervasive issue in the U.S. healthcare system is affordable access to healthcare, other core countries have different issues, and semi-peripheral and peripheral nations are faced with a host of additional concerns. Reviewing the status of global health offers insight into the various ways that politics and wealth shape access to healthcare, and it shows which populations are most affected by health disparities.