Early Life Conditions and Rapid
Demographic Changes
in the Developing World

There was a dramatic improvement in life expectancy during the twentieth century,
especially for those born between the 1930s and 1960s, primarily due to reductions
in infant and child mortality. Widespread public health interventions including
advancements in medical technology helped alleviate poor early life conditions –
serious infectious diseases, poor nutrition, and harsh living environments – by
reducing exposure to disease and treating it more effectively.1 In some developing
countries, this happened largely in the absence of improved standards of living.2
The dramatic increase in life expectancy was one of the demographic transitions of
the early twentieth century3 and partially explains the growth of aging populations
throughout the world, in particular in low- and middle-income countries in the early
twenty-first century.4 This growth is projected to increase the burden of disease due
to chronic conditions such as adult heart disease and diabetes—conditions which in
some instances originate in early life5—as populations age.6