The document discusses three key categories of factors that lead to differences in health between developed and less developed countries: social factors, economic factors, and environmental factors. Social factors include diet, lifestyle choices, and education. Economic factors include poverty/affluence and investments in healthcare and access to services. Environmental factors include living conditions, access to potable water, and proper sanitation. Overall, the document analyzes how each of these factors impact health and disease prevalence depending on a country's level of development.