America's lifespan has doubled since 1776 — experts reveal what changed

Americans today live roughly twice as long, on average, as they did when the Declaration of Independence was signed.

When the nation was founded in 1776, life expectancy was around 35 to 40 years old, historians estimate. However, someone who survived childhood in colonial America often lived into their 60s or even 70s.

Today, the average lifespan is about 79 years old, according to data from the Centers for Disease Control and Prevention.

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The improvement in lifespan over the centuries has been largely attributed to reduced deaths in infancy and from infectious diseases, multiple researchers have stated. Advances in sanitation, clean water, nutrition, vaccination and medical care have also contributed to lower mortality rates.

"Much of this vast discrepancy is related to the extremely high rates of infant, childhood and maternal mortality," Dr. Omer Awan, physician and professor at the University of Maryland School of Medicine, told Fox News Digital.

"Childbirth was dangerous, and without antibiotics and vaccines, many infectious diseases, such as measles, smallpox and pneumonia, were deadly," he went on. "Now we have cleaner water and sanitation, vaccines and antibiotics that have significantly prolonged life."

Advances in treatments of chronic diseases such as high blood pressure, cancer and diabetes have also significantly prolonged life, the Harvard-trained doctor noted.

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According to the CDC, improved prevention and treatment of high blood pressure has helped reduce deaths from heart disease and stroke, two of the nation's leading causes of death.

Mia Kazanjian, MD, a Stanford-trained body and breast radiologist with an interest in longevity who is based in Greenwich, Connecticut, attributes the shorter life expectancy in the 1700s to suboptimal sanitation, poor hygiene and limited medical treatments.

"Many babies and children died from infections like dysentery, diphtheria, scarlet fever and pneumonia," she told Fox News Digital. Children who survived into adulthood often succumbed to infections like tuberculosis, cholera and typhoid fever.

Maternal mortality has also fallen dramatically over the past century due to advances in antibiotics, blood transfusions and safer obstetric care, according to the CDC.

Kazanjian pointed to several key advancements over the centuries that contributed to longevity improvements, including the development of early municipal water systems that provided cleaner drinking sources.

"Sewer system networks were built, the first in Brooklyn in 1857," she said. "These allowed people to drink clean water and dispose of waste. Indoor plumbing with toilets and bathrooms became more widespread."

At this time, people’s understanding of disease started to improve, and public health measures were developed to minimize risk.

During the late 1800s, germ theory became widely accepted in medicine and public health, helping shape the Sanitary Era, the expert said.

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"The Federal Quarantine Act of 1878 allowed the government to prevent spread of infection from out of the country, from epidemics like yellow fever," she said. "Food safety regulations went into effect in 1906, when the Pure Food and Drug Act and Federal Meat Inspection Act were passed."

By 1900, the average life expectancy was about 49 years old, according to the National Vitals Statistics Report.

Another major landmark in increasing lifespan came with the development of vaccines and antibiotics to prevent and treat disease, Kazanjian noted.

"Jenner developed the smallpox vaccine in 1796, Pasteur created vaccines for rabies and anthrax in the 1880s, and several scientists created vaccines for polio, measles, influenza, mumps and rubella in the mid 1900s," she said.

"Antibiotics proliferated in the 1940s, specifically penicillin and tetracycline. By 1950, the US life expectancy was about 68 years old."

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From the mid-20th century to 2014, life expectancy continued to rise, Kazanjian said, largely due to "major gains" in medical knowledge of ways to prevent heart disease and stroke.

Public health campaigns promoting smoking cessation also played a role, as declining smoking rates helped reduce deaths from lung cancer, heart disease and stroke, according to the CDC.

"Motor vehicles became safer and carseats became staples," Kazanjian noted.

According to the National Institutes of Health, advances in emergency medical services and trauma care have substantially reduced deaths after serious injuries.

Development of pharmaceuticals for cardiovascular disease and cancer also contributed to longer lives, according to Kazanjian.

Modern longevity is more focused on preventing chronic disease and less about surviving childhood infections, noted Nneoma Oparaji, MD, a triple board-certified media physician specializing in obesity, lifestyle and internal medicine.

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"The next frontier will be less about living longer, but more about living healthier longer," Houston-based Oparaji told Fox News Digital.

Kazanjian pointed out that between 2014 and 2026, there has been a fall and a rise in lifespan.

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"The fall was due to young adult deaths from drug overdoses, particularly the opioid epidemic, suicides and alcohol-related deaths," she told Fox News Digital.

The COVID-19 pandemic reduced U.S. life expectancy by more than two years between 2019 and 2021 before it began recovering, CDC data shows.

Although U.S. life expectancy has rebounded since the pandemic, it remains below that of other high-income countries, largely because of higher death rates from chronic diseases, substance use and other preventable causes, according to KFF.

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Obesity rates also continue to climb, contributing to higher numbers of cardiovascular disease, diabetes and cancer, Kazanjian said.

"Most concerning is the rise in obesity in children," she added.

Changing cancer trends are also affecting lifespan among younger adults, data shows.

"My generation, the millennials, has seen an unprecedented rise in young adult cancers, particularly colon and breast," Kazanjian said, citing factors that include sedentary lifestyles, poor diet, alcohol, obesity and smoking, among others.

The doctor said she aims to raise public health awareness of ways to improve lifespan.

"We need to get off our screens, move around more, eat a whole food, plant-based diet, sleep seven hours a night, do our screening exams, and avoid toxins like alcohol and cigarettes."