Life expectancy has increased rapidly in the last 200 years. In 1800, life expectancy was around 30 years in all regions of the world. In the early 19th century, life expectancy began to increase in industrializing countries while it stayed low in the rest of the world.
Since 1900 the global average life expectancy has more than doubled and is now approaching 70 years. Today, no country in the world has a lower life expectancy than the countries with the highest life expectancy in 1800.
We can thank public health and improvements in then social determinants of health for most of the improvements. Deaths from infectious diseases declined drastically in the US during the 20th century, mostly (but not exclusively) because of the development of vaccines and mass vaccination programs. The development of antibiotics and improvements in housing and sanitation (environmental engineering) were also big factors.
Public health interventions contributed to a sharp drop in infant and child mortality and a corresponding 30-year increase in life expectancy. For example, in 1900 30% of all deaths occurred among kids less than 5. In 1900, the three leading causes of death were diphteria, pneumonia, tuberculosis, and diarrhea and enteritis.
The big drivers reducing childhood deaths were universal vaccination programs, improvements in sanitation and hygiene, and antibiotics. Public Health professionals played a major role in each of these areas and our public health programs today rest on their shoulders.
The CDC wrote a really good MMRW a few years ago called the 10 great public health achievements of the 20th century 10 Great Public Health Achievements of the 20th Century that identified the following public health interventions as the drivers of the increases in life expectancy and health outcomes. They are:
For a super interesting read about the improvements in global life expectancy visit the Our World In Data website.