With new medical breakthroughs happening every day, you might expect the human lifespan to keep rising over time. And according to a new study published in the Lancet, that may indeed be the case during the next two decades.
But the predicted increase in longevity isn’t as optimistic as some experts say it should be—especially not in the United States. And in some scenarios, they say, global life expectancy could actually decrease.
The analysis used data from 1990 to 2016 to generate forecasts about disease rates and life expectancy through 2040. Specifically, the authors looked at 250 causes of death, along with 79 independent factors that play a role in health, and made predictions for 195 different countries and territories.
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First, the good news: Around the world, most of the factors driving health and wellness were forecast to improve by 2040. On average, global life expectancy was predicted to increase by 4.4 years for men and 4.4 years for women.
But 36 out of those 79 drivers of health were forecast to get worse over time. Those included high body mass index (BMI), air pollution, high cholesterol, and some relating to dietary choices—like not eating enough whole grains and fruit. Overall, the factors that contributed the most to early death were high blood pressure, high BMI, high blood sugar, smoking, and alcohol use.
The top three causes of death in 2016—heart disease, stroke, and lower respiratory infections—are predicted to remain the same in 2040, according to the new study. COPD, road injuries, and diarrheal disease are also forecasted to stay in the top 10. But other leading causes of death—like malaria, preterm births, HIV/AIDS, and neonatal encephalopathy—are predicted to fall out of the top 10, to be replaced with chronic kidney disease, Alzheimer’s disease, diabetes, and lung cancer.
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The study also included models for “better” and “worse” health scenarios, based on the 85th and 15th percentiles, respectively, of past rates of change. In the “better” scenario, life expectancy would increase by about 7.8 years for men and 7.2 years for women. In the “worse” scenario, however, men’s life expectancy would actually decrease by about half a year, and would remain essentially unchanged for women.
On a country-by-country basis, the study predicted that Spain—followed by Japan, Singapore, and Switzerland—would lead global longevity in 2040, with average life expectancies exceeding 85 years. On the other end of the spectrum, Central African Republic, Lesotho, Somalia, and Zimbabwe would all have life expectancies below 65, “indicating global disparities in survival are likely to persist if current trends hold,” the authors wrote.
The United States falls somewhere in the middle of the 2040 projections, and is predicted to make slower gains than other countries. Between now and then it’s predicted to fall 20 places in the rankings—the biggest drop of all high-income countries—from 43rd to 64th place. The average American lifespan is predicted to increase from 78.7 to just 79.8.
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In an interview with The Guardian, study author Christopher Murray, MD, professor of health metrics sciences at the University of Washington, said that the United States has seen a “slowing down of progress” and has been “progressively underperforming compared to Europe” when it comes to life expectancy and overall health. He cites the impact of the opioid epidemic, as well as rising rates of heart disease and chronic respiratory disease.
This isn’t the first time in recent years the United States has gotten not-so-great news in this department. In 2016, it was reported that U.S. life expectancy between 2014 and 2015 had declined for the first time since the AIDS crisis in the mid-1990s. The following year, the trend was repeated.
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