Researchers suggest that radical life extension is unlikely in the 21st century and emphasize the need for significant institutional changes, such as in retirement planning and life insurance pricing if it does occur.
Study: Implausibility of radical life extension in humans in the twenty-first century. Image Credit: Solarisys/Shutterstock.com
In a recent study published in Nature Aging, researchers examined life expectancy by analyzing demographic data between 1990 and 2019. They found that although the 20th century saw significant improvements in life expectancy, the rate of improvements has lowered, indicating that in the absence of major advances in the field of aging, dramatic life extension is unlikely.
Background
Life expectancy before the 19th century was between 20 and 50 years, and the improvements in life expectancy were slow due to various plagues and pandemics. Major advances in health and medicine in the 20th century, in what came to be known as the “longevity revolution,” led to rapid improvements in life expectancy. What began with a decrease in childhood mortality later extended to middle and elderly adults, resulting in significantly higher life expectancy.
However, by 1990, various scientists believed that unless biological aging could be slowed, improvements in life expectancy had reached its limit. Contrasting opinions argued that continued technological and medical advances could still radically increase life expectancy.
The demographic trends from high-income countries from 1990 to the end of the second decade of the 21st century provide a suitable opportunity to determine whether the life expectancy of humans will continue to improve radically.
About the study
In the present study, the researchers used demographic data between 1990 and 2019 for long-lived populations from high-income countries such as Switzerland, Sweden, Spain, South Korea, Japan, Italy, France, Australia, the United States, and Hong Kong to examine hypotheses of radical life extension or limited lifespans.
The study used demographic survivorship metrics to assess trends in life expectancy and evaluate the possibility of radical life extension in long-lived populations. The central method employed by the researchers involved parameters such as life expectancy at birth, lifespan inequality, and life table entropy.
Life expectancy at birth is the number of years a newborn is expected to live, and the researchers calculated it using an age-specific survival function derived from population mortality data.
The distribution of deaths across different ages was indicated by life table entropy, with higher entropy indicating a greater variation in the ages at which people die. Lifespan inequality was a similar measure indicating a greater disparity in the age at which individuals die.
The researchers applied these metrics to populations that had the longest life expectancies. The Human Mortality Database, which provides mortality statistics for each nation, was the source of the demographic data, and the observed data, instead of future death rates, were used to assess mortality and life expectancy.
The researchers defined radical life extension as an annual increase of 0.3 years in life expectancy at birth. Data from 2019 for Japanese females was used to model a hypothetical scenario where the life expectancy at birth was 110 years, and the model adjusted death rates to estimate the future survival distributions.
Additionally, the researchers compiled a composite mortality schedule using the lowest age-specific death rates observed worldwide in 2019, not just in the high-income nations included in the study. This data excluded mortality due to coronavirus disease 2019 (COVID-19). These methods allowed the researchers to assess historical and recent longevity trends and enabled predictions of human lifespan changes in the future.
Results
The researchers found that only South Korea and Hong Kong showed a significant enough increase in life expectancy between 1990 and 2019 to be classified as “radical life extension,” amounting to a 0.3-year increase every year.
However, in Hong Kong, this increase was restricted to the early 1990s, which correlated to substantial tobacco control efforts and economic prosperity in the country. In all other countries included in the study, life expectancy improvements decreased over the last decade of the 20th century.
On average, between 1990 and 2019, the life expectancy in long-lived populations was found to increase by 6.5 years. However, the U.S. saw a decline in life expectancy in the second decade of the 21st century due to an increase in mortality rates among middle-aged individuals. This was worsened by the COVID-19 pandemic in 2019.
The study also indicated that the average probability of females born in 2019 surviving to the age of 100 is 5.1%, and for males, it is significantly lower at 1.8%. Hong Kong was found to have the highest survival rates until the age of 100 for females and males, at 12.8% and 4.4%, respectively.
The researchers deduced that mortality rates would have to decrease substantially to increase life expectancy by one year. For example, Japan would have to achieve a 20.3% reduction in mortality among females for their life expectancy to increase from 88 to 89 years, while male mortality rates in Japan would have to decrease by 9.5% to increase the life expectancy from 82 to 83 years.
The life table entropy values also indicated that it was becoming more difficult in the last three decades to increase the overall life expectancy. The lifespan inequality values suggested that people were dying within a narrower age range.
Conclusions
Overall, the findings from the study cumulatively suggested that the longevity revolution was drawing to a close and radical life extension would be difficult to achieve in the future without ground-breaking advances in aging and medicine.
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