They concluded Spain will overtake Japan's long-held position at the top of the world's life expectancy table in the next 22 years.
An average citizen in Spain can expect to live up to the age of 85.8 years old, according to a new study that predicted life expectancy around the world by 2040.
American scientists also noted that the decline in the growth rate of life expectancy can be fixed in some developed countries, e.g. the Netherlands, Canada, Norway.
The country with the longest longevity in 2016, Japan, will be replaced by Spain, which is now in fourth place and projected to enjoy an average life expectancy of 85.8 years in 2040. The study was published Tuesday in the journal The Lancet.
Japan, which sat atop the 2016 list, will fall to No. 2 at 85.7 years, followed by Singapore at 85.4.
In addition to Spain moving up on this list, it looks like China is also looking to see an increase in life expectancy, and dramatically so.
USA researchers said that by 2040, the life expectancy in different countries begin to increase. The World Economic Forum's Global Competitiveness Report, for example, recently listed Spain as one of the healthiest countries in the world.
According to the study, "The United States in 2016 ranked 43rd with an average lifespan of 78.7 years". The increase would put China in 39th place.
In 2016, the USA ranked 43rd among 195 nations with an average lifespan of 78.7 years.
As a result, in the worst-case scenario people born in Lesotho might have a life expectancy of only 45.3 years. Rounding out the rest of the bottom is the Central African Republic with a life expectancy of 58.4, Zimbabwe with 61.3 and Somalia with 63.6.
"The future of the world's health is not pre-ordained, and there is a wide range of plausible trajectories", said Dr. Kyle Foreman, Director of Data Science at the Institute for Health Metrics and Evaluation (IHME) at the University of Washington, and lead author on the study.