Extending Meaningful Longevity

Healthy Aging

Can we really extend human longevity?

In honor of Tuesday’s upcoming International Longevity Day, we thought it would be nice to apply a wider lens. While we often cover healthy aging science at the cellular and molecular levels, this week, let’s talk about how scientists, mathematicians, economists, and psychologists are approaching the concept of longevity.

Life expectancy was nearly 100% predictable using math.

As covered by Marchetti, life expectancy could be “precisely mapped with simple mathematics.” Basically, Marchetti hypothesized that the following three inputs determine how long we are expected to live:

• Hygiene. Reducing our exposure to harmful pathogens (bacteria, viruses, fungi, and parasites) helps us avoid infections that can kill us.
• Medicine. Improving our access to medications that effectively prevent, manage, treat, or cure otherwise fatal diseases will also stave off death.
• Lifestyle. How well we treat our bodies and minds via diet, physical and mental activities, community, and sleep determines how long we live.

When mapped over centuries, quantified concurrent advances in hygiene, medicine, and healthy lifestyles across these three areas indeed resulted in a remarkably clean and impressive upward trend of longer human life expectancy. Go, us.

This hypothesis, however, was published in 1994 – a time when heart disease deaths were wonderfully continuing to decline, smoking cigarettes on airplanes was in the midst of being banned (resulting in less lung cancer deaths), and more medicines were reaching more parts of the world. The trending arrow of life expectancy sure looked like it had plenty more room to go up and to the right.

Until it wasn’t (i.e., we hit the physical limits of longevity).

While Marchetti’s simple mathematical hypothesis of extending life expectancy worked over a period of two centuries, it seems to have hit a wall. Including a recent reversal of trends, where our life expectancies are declining, especially in the U.S.

Given the trends above, the question is: have we hit our maximum realistic human life expectancy limits? And instead of just seeing a bold increase in healthier older people, we are seeing a growing population of people who are not just older but are extraordinarily fragile and highly susceptible to sudden challenges (like COVID-19).

It seems that if we want to keep successfully pushing longevity up and to the right, we need to add a fourth component to Marchetti’s mathematical equation: Resilience. To meaningfully extend human longevity, we need to not just live longer, but to also maintain our physical resilience while doing so. In their paper on this topic, Zeng et al. conclude that “resilience significantly contributes to exceptional longevity.” Well, that’s encouraging.

The emotional cost of longevity (aka, our loss of satisfaction).

In the Journal of Population Economics, Nemitz published a paper in 2021 asking a key question: “Increasing longevity and life satisfaction: is there a catch to living longer?” Nemitz showed that while many people were living longer, they were becoming increasingly unsatisfied, especially during their last 5 years of life. The primary reasons for this dissatisfaction? Declining health and loneliness. This is why a good number of people say they are not necessarily interested in our current understanding of longevity. Why live longer if those added years are unhealthy and lonely?

Taken all of the above together, and maintaining Marchetti’s three pillars, we will likely need to accomplish the following to enable the next level of high-quality-of-life longevity:

• Slow the onset of chronic diseases.
• Fortify our resilience against the natural process of age-related frailty.
• Ardently protect healthy social communities, especially as we get older.

By doing so, we could not only continue to extend human longevity, but extend it meaningfully. For this International Longevity Day, let’s up the challenge to the fields of science, medicine, and sociology to meet these important needs for all of us.