Nancy Huang

Jun 27th 2022

Human Life Expectancy Continues To Increase


Through most of recorded history, human life expectancy was around 30 years. This was an average, so for every person who died as a newborn, there might be someone who lived to 60, or two people who lived to 45. In the late 1800s, life expectancy started to increase as humans developed a better understanding of how diseases spread and took measures to keep them from spreading. The 1900s saw efforts to reduce newborn and maternal mortality, and extraordinary advances in the prevention, diagnosis and treatment of communicable and non-communicable diseases.

How Has Life Expectancy Changed in the Last 100 Years?

Records from the United Kingdom show that life expectancy from 1543 through 1800 was between 30 and 40 years. It averaged just over 40 years until 1880 and then steadily increased. Life expectancy in the UK surpassed 50 years just after 1900, 60 years in the 1930s, 70 years in the 1950s and 80 years in the 2010s. Other modernizing countries soon followed suit. By 1950, the global average was 46 years, and it’s now over 70. Developing countries — particularly in sub-Saharan Africa — have lagged behind but are making progress. In 2019, the Central African Republic had the lowest life expectancy at 53 years.

Some of the greatest gains have been in the survival of children. Through most of human history, about 25% of people died as infants in the first year of life, and about 50% died as youths before reaching the age of 15. According to Our World in Data, this was seen in a wide variety of cultures, including Ancient Greece, Ancient Rome, the Americas before Columbus, Medieval Japan, Imperial China and Renaissance Europe.

In 1800, about 43% of children worldwide died before the age of 5. That number decreased to 36% in 1900, 24% in 1940, 9.3% in 1990 and 4% in 2017. In highly industrialized countries, less than 1% of children now die before the age of 5, with a few countries averaging below 0.25%. In sub-Saharan Africa, there are still countries where more than 10% of children die before their fifth birthday.

Survival has increased across all age groups. In 1900, life expectancy in the United States was 48 years, according to Statista, with the leading causes of death being communicable diseases, including influenza, tuberculosis and gastrointestinal infections. Today, life expectancy in the US is 78.7 years old, and the leading causes of death are non-communicable diseases, including cardiovascular disease and cancer.

Four major factors have contributed to this remarkable increase in human life expectancy: (1) maternal and newborn care, (2) clean water and sanitation, (3) vaccines and antibiotics for infectious diseases, and (4) prevention and treatment of non-communicable diseases.

Improving Maternal and Newborn Care

In the 1800s, Finland had more than 800 maternal deaths per 100,000 live births. The United States had similarly abysmal numbers into the 1900s. The maternal mortality rate is now as low as 3 deaths per 100,000 live births in the developed world (including Finland), and as high as 1,360 deaths per 100,000 live births in Sierra Leone.

The techniques used to reduce maternal mortality in the late 1800s still apply today. Prenatal care can prevent or identify problems before they become too serious. Washing hands and sterilizing medical equipment can prevent bacterial infections, the most common cause of maternal deaths. In 1945, the antibiotic penicillin became available and made C-sections much safer.

Better maternal care also reduces infant mortality. Babies are less likely to suffer birth injuries and less likely to be delivered early. For newborns, small differences in body size and lung function can be the difference between life and death. Nonetheless, effective treatments can be surprisingly simple. “Kangaroo mother care” — when an infant is held skin-to-skin with their mother — helps the baby maintain body temperature and can improve milk production and nursing. When there is a risk of early delivery, two doses of steroids can accelerate the baby’s lung development.

Infants and young children are especially vulnerable to infectious diseases, which can spread easily if clean water and sanitation are lacking.

Access to Clean Water and Sanitation

Infectious diseases were responsible for 45% of deaths among children under 5 in 2017. Lower respiratory infections and diarrheal diseases were the most deadly and still rank among the top 8 causes of death in adults.

Many infectious diseases can spread through unwashed hands and contaminated water, so providing access to clean water and sanitation has been a major priority. According to Our World in Data, 39% of people did not have access to safely managed drinking water in 2000, and that number is now 25%. In 2000, 71% of people did not have access to safely managed sanitation, and that number is now 46%. Notably, 6% of the population still practices open defecation. So much progress has been made, but much work remains to be done.

Vaccines and Antibiotics for Infectious Disease

Vaccination is perhaps the most successful and cost-effective medical intervention ever. Consider smallpox, which killed 300 million people in the 20th century alone. After a global vaccination effort in the 1960s and 1970s, the last naturally occurring case of smallpox was reported in 1977.

Other vaccines have undoubtedly altered the course of history by targeting polio, tetanus, measles, mumps, rubella, whooping cough, rotavirus, diphtheria and coronavirus (which causes COVID-19). You likely know a lot about one of these diseases, and very little about the others. For that, you can thank the effectiveness of vaccines.

Some vaccines target diseases that impact specific geographic areas (e.g. dengue, Japanese encephalitis), affect small numbers of people (e.g. rabies), or cause harm years after the initial infection (e.g. Human papillomavirus). Most vaccines target viral infections, while antibiotics are highly effective against bacterial infections.

Preventing and Treating Non-communicable Diseases

How has life expectancy changed in the last 100 years? People are living longer and longer. Data from England and Wales shows that in 1851, only 70% of people made it to their 10th birthday, only 47% reached 50, and only 20% reached the age of 73. In 2011, 97% reached age 50, 80% reached 73, and 50% could expect to live to 84.

People are now contending with diseases of old age, wealth and bad habits, (such as high-fat diets). The top 10 causes of death worldwide now include heart disease, stroke, cancer, Alzheimer’s disease and diabetes. The medical community has developed effective ways to screen for risk factors. Routine screenings include blood pressure, blood sugar, cholesterol levels, pap smears, colonoscopies, etc. Early detection and better treatments have improved survival.

With all of these advances, the process of preventing, detecting and treating these diseases may soon feel as mundane as washing your hands with soap and water.

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