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The sharp rise in life expectancy over the past century is finally slowing down – and will stop when the average life expectancy reaches 87 – according to a new study of expected lifespans between 1990 and 2019.
The study, published last week in Nature Aging, by gerontologist Jay Olshansky and several co-authors, found that the rise in life expectancy during the 20th century has slowed down markedly over the past 30 years.
It looked at data on life expectancy at birth collected between 1990 and 2019 from the eight countries with the highest life expectancies – Australia, France, Italy, Japan, South Korea, Spain, Sweden and Switzerland. It also examined lifespans in Hong Kong and the United States.
The new study follows on from research that Olshansky, now professor of epidemiology and biostatistics at the School of Public Health, University of Illinois in Chicago, undertook before 1990. The average life expectancy for the world as a whole is currently 72.
Olshansky argued in 1990 that the world was approaching the end of a “longevity revolution” – and that there was only a certain distance medicine could take us before we succumb to the ageing process anyway. His latest study provides more concrete evidence to back up this claim.
Why has life expectancy risen so much in the past century?
About 100 years ago, in the late 19th and early 20th centuries, the average life expectancy was approximately 50 years. By 1990, this had risen to about 70 – and was as high as the mid-80s in richer countries – following what researchers call a “longevity revolution”.
Advances in medical care which prevented infant deaths and the deaths of women during childbirth, in particular, were responsible for the first longevity revolution which saw life expectancy for men and women rise dramatically because women and children who would previously have died early in life were now living to a “normal” age.
“You can save children only once, and once you’ve done it, these children who ordinarily would have died at much younger ages, are now living much, much longer than would have been the case,” Olshanksy explained.
Since the end of the 20th century, the medical industry has turned its attention to diseases and disorders that have become more prolific because we are living longer, including heart disease, cancer, stroke and Alzheimer’s disease. People are now also surviving these conditions as a result of better medicine.
What does the new study show?
The study examined data on life expectancy at birth collected between 1990 and 2019. The study deliberately stopped at this year to strip out any artificial dampening caused by the COVID pandemic.
The “upper average” life expectancy has already passed 85 in some of the richer countries studied – about 88 for women and 82 for men.
The new study predicts that the maximum life expectancy will stop at about 87 years – 84 for men and 90 for women – which some countries are already close to achieving. After that, however, the average age at death would stop rising.
The focus of the study was what scientists call “life table entropy”, which suggests that there are limits to how far the longevity revolution can go.
“When you live out to these later and later ages, into your 70s, 80s, 90s, 100, you run into a problem,” says Olshansky. “That problem is the biological process of ageing itself, the ageing of our cells, tissues, organs, organ systems that we call senescence.
“So when you push out survival into an age window where they run up against an immutable force of biological ageing, the rise in life expectancy must slow down.”
Ultimately, the study showed that the only way to extend lifespans from this point on is to slow the ageing process itself.
Can we slow the ageing process?
Due to advances in medical technology, life expectancy will more than likely continue to nudge up, but there still remains a ceiling due to natural ageing. Therefore, the next step to continuing the “longevity revolution” is to slow the process of ageing itself, something Olshansky says he is “confident” could happen. It is certainly something being studied.
“Given rapid advances now occurring in geroscience, there is reason to be optimistic that a second longevity revolution is approaching in the form of modern efforts to slow biological aging, offering humanity a second chance at altering the course of human survival,” the study states.
Geroscience is the study of the biological process of ageing; in short, what makes our bodies age.
According to researchers, they can also study healthy centenarians (those who have reached the age of 100 years) and supercentenarians (those above 110 years) to understand the underlying conditions and environment that have contributed to their long lifespan.
Some individuals who live to old age may possess a genetic signature of sorts, further study of which may provide answers to the question of what causes longevity.
“There are likely to be specific genes that they possess that produce proteins in their body that protect them from the things that kill the rest of us at younger ages,” says Olshanksy.
The study of other animals which have long lifespans may also offer insight. “This is one of the reasons why scientists want to study other long-lived species. How is it possible for a bowhead whale to live for 210 years? How is it possible for a Greenland shark to live for 500 years?” he added.
What did the study tell us about individual countries?
The study also revealed outcomes that were specific to countries. Although it is unclear as to the root cause of this discovery, Hong Kong is experiencing a stronger continuation of the increase in life expectancy than most countries.
The study found: “The highest population-specific probability of surviving to 100 occurred in Hong Kong where 12.8 percent of females and 4.4 percent of males are expected to reach age 100 in their lifetime based on life tables from 2019.”
According to the most recent World Bank data from 2022, the average life expectancy for Hong Kong is 84 years while the average life expectancy for the world is 72 years.
In the study, a life table shows the probability of surviving or dying at different ages across a particular population.
The study revealed the improvement in life expectancy in Hong Kong was due to economic prosperity and smoking bans put in place between 1990 and 2000.
However, in all countries, including Hong Kong, China’s self-governing territory, “the most recent decade of change in life expectancy is slower than it was in the last decade of the 20th century”, the study concluded.
Of the 10 countries studied, the US showed the slowest improvement in life expectancy. According to 2022 World Bank data, the average life expectancy in the US is 77 years.
Why is life expectancy slowing in the US particularly?
Olshanksy attributes some of the slowing down of life expectancy in the US to the lack of access to universal healthcare. The US operates an insurance-based system of healthcare, unlike the vast majority of Western countries, where healthcare is mostly funded by taxation and accessible by all. The bifurcation between those who have access to high-quality healthcare and those who don’t in the US is stark. One subgroup of the population is therefore bringing down the overall average in the US due to disparities in quality healthcare.
“One population subgroup, which is wealthy, highly educated, they have access to healthcare, they take their medications when they see their doctor, they actually go see their doctor, they have access to doctors. Now you’ve got this other subgroup of the population, which is much larger than the first one, and this other subgroup of the population is less educated, they have less access to healthcare,” says Olshansky.
