How long can we live? Despite impressive public health and medical advances, life expectancy gains are markedly slowing

A recent study led by the University of Illinois at Chicago, in collaboration with the University of Hawaiʻi John A. Burns School of Medicine (JABSOM), the Kuakini Honolulu Heart Program Center of Biomedical Research Excellence - Center for Translational Research on Aging (Kuakini HHP COBRE-CTRA), UCLA and Harvard Medical School, indicates that the significant rise in global life expectancy (LE) observed throughout the 19th and 20th centuries has notably decelerated.

Why? The analysis found that despite major advances in lowering infant mortality and late-life mortality, due to improved public health and preventive medicine, life expectancy at birth in the world's longest-living populations has increased a mere 6.5 years since 1990. In essence, the easy gains with current technology and medical care appear over. 

This markedly slower increase in life expectancy has shocked many demographers, many of whom have used the popular “continual increase in LE model.” This model extrapolates future life expectancy trends from past experience to manage expectations regarding the future solvency of popular American social programs. Given that this model has not correctly predicted LE gains over the past several decades there are major public health implications. For example, public servants who use this model, despite their best efforts, may have markedly overestimated the costs to maintain Medicare/Medicaid, Social Security, and other public health programs. 

The current Nature Aging paper "Implausibility of Radical Life Extension in Humans in the 21st Century" presents new evidence suggesting that humans are nearing a natural biological “limit” to life expectancy. Unless novel gerotherapeutic interventions are discovered and become widely available - that slow aging at the molecular and biological level.

Lead author, S. Jay Olshansky of the University of Illinois Chicago School of Public Health, stated that the most significant advances in longevity through medical breakthroughs have already been achieved.

"Most people alive today at older ages are living on time that was manufactured by medicine," said Olshansky, a professor of epidemiology and biostatistics. "But these medical band-aids are producing fewer years of life, implying that the rapid increase in life expectancy is now documented to be over. It also means that further life extension through disease reduction may even be harmful if it isn't accompanied by healthy life. We should now shift our focus to efforts that slow the effects of aging and extend healthspan." 

The analysis, conducted with JABSOM and Kuakini’s Dr. Bradley Willcox, and additional colleagues at UCLA and Harvard, is the latest chapter in a three-decade debate over the potential limits of human longevity. 

In 1990, Olshansky and colleagues published an important manuscript in Science that argued humans were approaching a ceiling for life expectancy of around 85 years and that the most significant gains had already been made. Others predicted that advances in medicine and public health would accelerate 20th-century trends upward into the 21st century - which has important Social Security and other public health implications.

Thirty-four years later, the evidence reported in the current 2024 Nature Aging study strongly suggests life expectancy gains will continue to slow as longer-living humans become more exposed to the damaging effects of aging. The study looked at data from the eight longest-living countries, Hong Kong, and the U.S. While the long-lived locales had markedly slower LE gains, American life expectancy actually decreased over this period. 

"Our result overturns the conventional wisdom that the natural longevity endowment for our species is somewhere on the horizon ahead of us – a life expectancy beyond where we are today," Olshansky said. "Instead, it's behind us – somewhere in the 30–60-year range. We've now proven that modern medicine is yielding incrementally smaller improvements in longevity even though medical advances are occurring at breakneck speed." 

Dr. Olshansky believes that these findings will affect wealth management and life/long-term care insurance firms, which increasingly base calculations on the assumption that customers will live 95-plus years.

“This is profoundly bad advice because only a small percentage of the population will live that long in this century," Olshansky said. 

“These findings have incredible importance for all of us,” Dr. Willcox said. “How do we realistically plan for our retirement? First, what data source do we trust to plan how long we might live? Second, how much must we save for basic living expenses, health care, life insurance, long term care insurance, vacation dreams and/or provide an inheritance for our children and grandchildren?

More scientific investment should focus on understanding geroscience and developing gerotherapeutics. Geroscience is about better understanding the molecular and biological aspects of aging so that we can optimize the “hallmarks” of the aging process (gerotherapeutics) - before age-related diseases manifest. Hallmarks of mammalian aging such as inflammation, mitochondrial dysfunction, telomere damage are likely amenable to early interventions, which may slow the aging process itself. This, potentially, may yield decades of additional healthy lifespan. This will take years and perhaps decades to manifest, Dr. Willcox said. While we continue to research such interventions, there is more immediate potential in improving quality of life at older ages - instead of extending life without concomitant health. 

"This is a glass ceiling, not a brick wall," Olshansky said. "There's plenty of room for improvement: for reducing risk factors, working to eliminate disparities, and encouraging people to adopt healthier lifestyles – all of which can enable people to live longer and healthier. We can push through this glass “health and longevity ceiling” with geroscience and efforts to slow the effects of aging." 

Dr. Bradley Willcox agrees. He notes “we have studied human aging with a cohort of 8,000+ Japanese-American men in Hawaiʻi for nearly 60 years, and their offspring. We discovered several potential gerotherapeutic agents, several of which are in clinical trials. For example, we found that a single human gene - FOXO3 – is associated with 2-3 times the probability of becoming a centenarian. One third of us have the “longevity version”. What about the rest of us? Well, the usual version can be activated by several different compounds, such as astaxanthin, and could potentially yield similar benefits as the longevity version. We and our research partners are testing promising gerotherapeutic agents to help more of us replicate this amazing increase in lifespan and healthspan - stay tuned”. This is just the beginning of potential gerotherapeutic breakthroughs at our Hawaiʻi-based Center of Excellence on Aging.