The number of people reaching 100 years old in the United States may not grow as much as previously thought, according to new research. Centenarians currently make up only a small fraction—0.03%—of the U.S. population, and earlier projections had suggested this could quadruple in coming decades based on census data from the Pew Research Center.
However, an international group of researchers now says that more recent generations are less likely to become centenarians than those born before 1939. The study was published August 25 in the Proceedings of the National Academy of Sciences and included cohorts from 23 high-income countries, including the United States, Australia, several European nations, Canada, and Japan.
“The unprecedented increase in life expectancy we achieved in the first half of the 20th century appears to be a phenomenon we are unlikely to achieve again in the foreseeable future,” said Héctor Pifarré i Arolas from the University of Wisconsin-Madison. “In the absence of any major breakthroughs that significantly extend human life, life expectancy would still not match the rapid increases seen in the early 20th century even if adult survival improved twice as fast as we predict.”
Researchers found that before 1938, average life expectancy increased by about 5.5 months per generation across these countries. Between 1900 and 1938, life expectancy rose sharply from 62 years to around 80 years. Much of this gain came from medical advances that reduced infant mortality rates.
Since infant death rates have remained low for decades in wealthy nations, further gains in overall longevity have slowed down. From 1939 to 2000, each generation added just between 2.5 and 3.5 months to their expected lifespan—a smaller increase than before.
“We forecast that those born in 1980 will not live to be 100 on average, and none of the cohorts in our study will reach this milestone,” said José Andrade of the Max Planck Institute for Demographic Research. “This decline is largely due to the fact that past surges in longevity were driven by remarkable improvements in survival at very young ages.”
Unless there is a major breakthrough such as cures for cancer or heart disease—the leading causes of death—the rate at which average lifespans grow is expected to keep slowing down.
Currently, Americans can expect an average lifespan of about 78.4 years: men at roughly 75.8 years and women at about 81.1 years, according to Centers for Disease Control and Prevention data (https://www.cdc.gov/nchs/fastats/life-expectancy.htm). Although Americans tend to live shorter lives than Europeans (https://www.mcclatchydc.com/news/nation-world/national/article286797110.html), researchers noted that stagnant or slowing increases in life expectancy are being seen across Europe as well.
The study authors emphasized that factors like pandemics or new treatments could affect future trends but cannot be reliably predicted over long periods.
“Although a population-level analysis, this research also has implications for individuals, as life expectancy influences personal decisions about saving, retirement and long-term planning,” according to the release. “If life expectancy increases more slowly as this study shows is likely, both governments and individuals may need to recalibrate their expectations for the future.”
The research team consisted of Arolas, Andrade and Carlo Giovanni Camarda.
