The significant increase in life expectancy in developing nations is primarily due to?

The significant increase in life expectancy in developing nations is primarily attributed to the epidemiological transition. This concept refers to the shift in the pattern of diseases and health issues that occur as a country develops. In the early stages of development, populations often face high mortality rates due to communicable diseases and poor health conditions. As medical advances are made, public health policies improve, access to healthcare increases, and vaccination programs become widespread, the burden of infectious diseases declines significantly.

Simultaneously, improvements in sanitation, nutrition, and access to clean water contribute greatly to reducing disease prevalence. The decline in mortality from infectious diseases and the corresponding increase in life expectancy during this transition are pivotal. Thus, as developing nations experience this shift, they see a marked increase in the average lifespan of their populations.

In contrast, options referring to socioeconomic or demographic transitions focus on different aspects of societal changes—economic development or shifts in population structure—rather than the direct impact of health improvements on life expectancy. Cultural transitions, while they may influence health practices, are not the primary drivers for the drastic improvements in life expectancy observed due to health and disease control measures.