A new study published in Nature Aging indicates that we may have reached or are approaching the maximum possible average life span. This is based on life expectancy data collected from 1990 to 2019 from countries with the highest longevity, Australia, France, Italy, Japan, South Korea, Spain, Sweden, Switzerland and Hong Kong. Even though life expectancy continues to rise, the rate of increase has slowed.
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At the turn of the 20th century in the United States for example, life expectancy at birth was only 47.3 years. By 2000, this number had skyrocketed to 76.8 years.
This was common across other high-income countries including Australia, France, Italy, Japan, South Korea, Spain, Sweden, Switzerland and Hong Kong.
Early medical interventions and vaccinations reduced the number of deaths from infectious diseases. As medical advances continued, people were living longer even into their middle and older years, as life-threatening diseases like heart disease became more manageable.
The new study suggests that the 21st century will not see such increases in life expectancy. The researchers found that since 2010, the rate of life expectancy growth has slowed in most of the ten wealthy countries they analyzed especially in the US.
The study predicts that people in high-income countries may only gain an additional 2.5 years of life expectancy over the next three decades.
Current birth cohorts have only a small likelihood of reaching age 100 with women having a 5.1% chance and men only 1.8%.
In contrast to the 20th century, where every decade added three years to life expectancy, future gains are expected to be much smaller.
The primary reason for this slowdown in life expectancy growth, according to the researchers is that we may be approaching the biological limit of human longevity.
While advancements in medical science can address specific diseases or conditions, we have yet to conquer the aging process itself.
As more people survive to older ages, the biggest risks for death come from biological aging. The gradual wear and tear on cells, tissues and organs becomes increasingly difficult to stop or reverse.
While we’ve managed to reduce deaths from infectious diseases and chronic conditions, we can’t yet halt the biological clock that ticks after age 60 or 70.
According to Jay Olshansky, lead author of the study and professor of epidemiology and biostatistics at the University of Illinois Chicago tackling individual diseases like Alzheimer’s disease or cancer is like putting a temporary survival Band-Aid on the problem.
The study addresses that more focus should be placed on geroscience, the study of the biology of aging. Rather than targeting diseases one by one, geroscience aims to address the root causes of aging, slowing down or reversing the aging process.
For example, scientists are researching drugs that could extend the life of telomeres, the protective caps at the ends of chromosomes. These telomeres naturally shorten over time contributing to aging and cell death.
By maintaining their length, scientists hope to extend the healthy lifespan of cells and in turn, human life. Olshansky argues that if we want to see gains in life expectancy, we need to focus on creating what he calls the most precious commodity on Earth, healthy life.
The study analyzed life expectancy data from nine wealthy regions (Australia, France, Italy, Japan, South Korea, Spain, Sweden, Switzerland and Hong Kong) and the United States.
Overall improvements have decelerated in most countries after 2010. Hong Kong was the exception, where life expectancy growth accelerated during this period, though the reasons behind this remain unclear.
One hypothesis is that Hong Kong’s healthcare access may have improved, allowing more people to live longer. United States life expectancy is lagging largely due to the opioid crisis and other socio-economic factors.
Life expectancy for men may never exceed 84 years, while for women, it may max out at 90 years. The likelihood of newborns today living to 100 is slim with only a 12.8% chance for females in Hong Kong and a 4.4% chance for males.
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During the 20th century, advances in medicine and technology such as water sanitation, antibiotics and vaccines, caused life expectancy to rise.
At the start of the century, life expectancy was around 30 years. By 2021, this number had surged to over 71 years globally. The rise was in developed countries, where life expectancy increased by about three years per decade.
While earlier medical interventions had effects on reducing infant mortality and combatting infectious diseases, modern medicine’s ability to extend life expectancy by treating chronic diseases like cancer, heart disease and diabetes has begun to show diminishing returns.
Dr. Olshansky refers to these efforts as Band-Aids, effective but limited in their capacity to push human life expectancy much beyond current levels.
One of the conclusions of the study is that even if we eliminated deaths from external causes like accidents or common diseases before the age of 50, the average life span would only increase slightly by one year for women and one and a half years for men.
As we age, the declining function of internal organs and systems like the cardiovascular and immune systems becomes inevitable.
This biological wear and tear make it unlikely that most humans will live much longer than they currently do, regardless of medical advancements.
One of the findings of the research is what is known as the compression of mortality. This concept refers to the shrinking window during which most people die, meaning that rather than more people living to 100 or beyond, the age of death for most individuals has become more tightly clustered around 70 to 90 years.
The researchers calculated that even if we were able to eliminate diseases such as cancer and heart disease or prevent all deaths before the age of 50, life expectancy would increase only marginally.
This reality points to the conclusion that while modern medicine can extend the average life span by a few years, it cannot radically change the biological process of aging itself.
While Dr. Olshansky and his team argue that we’ve essentially reached the upper limit of human life expectancy, not all scientists agree.
Dr. Luigi Ferrucci, the scientific director at the National Institute on Aging suggests that investment in preventive health could delay the onset of age-related diseases. He believes this could reduce the biological damage caused by aging and slightly extend life expectancy.
Dr. Ferrucci’s argument focuses on measures like improving diet, exercise and early detection of diseases, which could help people live healthier lives for longer, though he acknowledges this will not push the ceiling of human life span.
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