What’s killing Americans and driving down life expectancy?

In a recent study in The Lancet, researchers predicted that by 2040, people the world over will be living longer. In extreme cases, such as Syria and Nigeria, the researchers projected life expectancy to increase by as many as 10 years. But in the United States, they estimated that it will rise by only 1.1 year—putting the United States in the bottom five of all countries in terms of life expectancy growth by 2040.

In 2016, the United States ranked 43rd among all nations’ life expectancies, with an average lifespan of 78.7 years. But in 2040, life expectancy in the United States is forecast to be only 79.8 years, falling to a rank of 64th among all nations—the biggest drop in rank among high-income countries.

For comparison, China ranked 68th in 2016, with an average life expectancy of 76.3 years. But if recent health trends continue through 2040, China could rise to a rank of 39th, with an average life expectancy of 81.9 years—a 5.6-year increase in lifespan, the researchers predicted.

In fact, China would be one of 59 countries that could have a life expectancy of more than 80 years by 2040. In Japan, Singapore, Spain, and Switzerland, life expectancy is estimated to be greater than 85 years.

Now, what’s the life expectancy again for Americans in 2040? Oh yeah, 79.8 years.

What’s driving us down?

In the coming years, study researchers anticipate a shift in premature death from communicable to non-communicable diseases (NCDs), including diabetes, chronic obstructive pulmonary disease (COPD), chronic kidney disease, and lung cancer—not to mention worsening health outcomes related to obesity.

But NCDs and worsening health aren’t inevitable, the researchers noted. People can still learn to make changes to avoid these outcomes. For example, one bright spot for the United States was that it was one of only 20 countries that reduced the population’s risk of exposure to tobacco faster than 2% between 1990 and 2016.

“The future of the world’s health is not preordained, and there is a wide range of plausible trajectories,” said the study’s lead author Kyle Foreman, PhD, MPH, director of data science, Institute for Health Metrics and Evaluation, University of Washington, Seattle, WA. “But whether we see significant progress or stagnation depends on how well or poorly health systems address key health drivers.”

The top three health drivers behind the future trajectory for premature mortality will be metabolic factors—high blood pressure, high body mass index, and high blood sugar, Dr. Foreman and coauthors predicted. Other top drivers of premature mortality will be tobacco and alcohol use, and air pollution.

These drivers will change the causes behind shortened lifespans. In 2016, for instance, the top 10 causes of premature death in the United States were ischemic heart disease, lung cancer, COPD, stroke, road injuries, Alzheimer’s disease, suicide, drug use, colon and rectal cancer, and lower respiratory infections.

In 2040, however, the leading causes are expected to be ischemic heart disease, Alzheimer’s disease, lung cancer, drug use, chronic kidney disease, road injuries, colon and rectal cancer, COPD, lower respiratory infections, and diabetes mellitus.

A huge effect on the future of health care

These changes will have a serious impact on the allocation of health care resources—and may also shift the focus of medical curricula and health-care occupations, the researchers predicted.

“Our forecasts of the rapid rise for several NCDs, including COPD, diabetes, chronic kidney disease, Alzheimer’s disease, and lung cancer, portend serious health system implications,” wrote Dr. Foreman and coauthors. “To the extent that increasing YLLs [years of life lost] signal rising disease occurrence and increased demand for health care, these shifts could have significant ramifications on the volume and type of health expenditure in many health systems.”

But, again, these developments are not inevitable, the authors concluded.

“Policy today can have a huge effect on the future. Funding of public health and medical care, social policy and multisectoral action for health can have profound effects on both short-term and long-term outcomes,” they wrote. “Most importantly, our study shows that the future is highly malleable, but also requires concerted attention and continued prioritization of the key drivers of health.”