Research on Valuing Additional Life Years

Examining societal perspectives on longevity

Introduction

How do we evaluate the trade-offs for extending lifespan?

Financial analysts and economists often note that this question requires additional context. Key considerations include the timing of the life extension and the quality of the additional time gained.

Consider two scenarios for analysis: A hypothetical individual, age 50 and in good health, facing different life expectancy projections. In the first case, the extension would apply to the immediate future. In the second case, the extension would apply thirty years later. The perceived value of the extension likely differs significantly between these scenarios.

This difference in valuation based on temporal proximity exemplifies the economic concept of time preference. This principle helps explain why market interest rates tend to be positive in free market conditions[^1].

I have been thinking about the value of extra years of life—and you might be surprised by what I’ve learned.

Longevity

I recently finished Outlive, The Science and Art of Longevity by Peter Attia, MD with Bill Gifford.

The book is well-written (despite its habitual use of acronyms that force the reader to constantly flip back to decipher terms like “WHI,” “NNT,” “CGM,” “MUFA,” “SFA,” and dozens of others) and covers a lot of ground. Its implicit promise is that if you take the right actions, you’ll live longer. (I recommend the book if that interests you—even though no one really knows for sure if it “works.”)
Let’s assume it does.

Is Implementing the Program Worth It?

In this post I want to address a question that I haven’t seen discussed elsewhere: Is it worth it? In other words, is the benefit of following Attia’s program—or a similar exercise regimen—worth the cost of doing so?

Attia’s hypothesis is that most people can choose behaviors that will maximize their chances of living a long, high-quality life. The majority of the book addresses what he identifies as the four largest medical risks for dying:

  1. Atherosclerotic disease (heart disease and strokes)
  2. Cancer
  3. Neurodegenerative disease (e.g., Alzheimer’s)
  4. Metabolic disease (elevated insulin, fatty liver, and type 2 diabetes)

After outlining what’s known (and not known) about these diseases, Attia turns to actions we can take—or avoid—that he believes[^3] will reduce each risk. Drawing on his extensive knowledge of the scientific literature and his experience treating thousands of patients, he focuses on five areas:

  • Exercise
  • Sleep
  • Nutrition
  • Drugs and supplements
  • Mental health

(They are apparently listed in order of their expected efficacy.)

In particular, Attia believes that exercise is the most potent action most people can take to extend both the quantity and quality of life. He further suggests that getting enough sleep—simplified here to 8 hours a night—is the second most powerful tool.

For the sake of the following analysis, I will consider only exercise and sleep.

What Does It Cost?

For most people[^4], the major cost of implementing the “Outlive” program is time. Attia recommends:

  • A minimum of about 3 hours per week of exercise for beginners.
  • He himself spends 6 hours per week in the gym[^5].
  • In one of his podcast episodes[^6], he appears to state that his program requires a total of about 9 hours spread over the week.

If you wouldn’t otherwise exercise and decide to do so in hopes of reaping future rewards (i.e., more years of life), the hours you spend exercising can be viewed as a cost from an economic perspective[^7]. However, those same hours can also be seen as an investment[^8]. In this analysis, we use the range of 3 to 9 hours per week as the investment for implementing the exercise portion of the Outlive program.

What’s the Payoff?

The implicit promise of the program is that you’ll live longer—but how much longer? This is a critical question that is not always explicitly addressed.

  • Attia is 50. The life expectancy for an American male like him at age 50 is about 30 more years (i.e., to age 80)[^9].
  • Suppose Attia expects to live to age 88[^10].

Attia is not pulling the extra 8 years out of thin air. A 2022 study[^11] published in the British Journal of Sports Medicine reported that “weightlifting”[^12] was associated with a mean extra 9 years of life in its questionnaire-based study of 99,713 adults. The estimated interquartile range of additional years was 7.6 to 10.6 years[^13].

What’s the Return on Investment?

While there’s much more to exercise than simply putting in hours, for tractability I will look at the investment of hours now for the payoff of more years of life later. We can use standard present value analysis—except here the “currency” is hours, not dollars.

Base-Case Assumptions

  1. A 50-year-old male who doesn’t exercise can expect to live to age 80.
  2. The same male, by investing 8 hours per week in exercise, can expect to live to age 88.
  3. Investment and return are measured in hours per year.
  4. We assume people value their waking hours (sleeping 8 hours a night—but we do not count sleep as “return”).
  5. The exercise regimen continues every year, even after age 80.
  6. The exercise costs only the time allocated to it and provides only the expected extra years of life (i.e., no additional “disutility” or “utility” beyond life extension benefits[^14]).
  7. Everything else remains constant.

Under these assumptions, the computed rate of return is 5.8%.

Sensitivity Analysis

  • If 6 hours per week yield 6 extra years (75% of the benefit), the return is 6.1%.
  • If 3 hours per week yield 4 extra years, the return is 6.5%.

Note: These returns are based on estimates; we simply don’t have data precise enough to be certain. The analysis gives a “ballpark” estimate.

Click here to request a table of sensitivity analysis covering investments from 3 to 10 hours per week and extra years of life from 2 to 10.

Keep in mind that much remains unknown about how our actions (or inactions) affect life expectancy. Even “facts” are often debatable. For example, I once believed that the oldest documented human life was that of Jeanne Calment (122 years). However, Attia reports that a 2019 paper[^17] claims that Jeanne Calment was actually her daughter—23 years younger. If true, the “oldest person ever” lived to 99, not 122. The point is that even historical “facts” can be hard to grasp.

Roger Silk’s Economic Perspective

Roger Silk does some math, attempting to think like an economist.

His basic model assumes that we value 16 waking hours per day. Exercise costs time now and pays off with additional time in the future. He then asks: if a program of 9 hours gives a 50-year-old the chance to live to 88 instead of 80, what is the rate of return? He finds 5.8%, with returns up to 6.5% for smaller investments—suggesting that the marginal return on the final hours is likely closer to 4%.

Is that a good investment? As Roger points out, there is no “inflation” in years. If all things were equal—if only my personal time discounting mattered, and postponing my actions did not impact the world—I would take essentially any positive return.

Key Considerations Being Ignored

  1. Correlation is not causation.
    Although exercise is associated with 8 extra years of life (PubMed), this is almost certainly an overstatement of the causal effect. Better exercise is correlated with good health and other beneficial habits, and the study shows little effort to control for these confounding factors.

  2. Exercise has benefits beyond lifespan extension.
    Personally, exercising gives me more energy, improves my mood, enhances my appearance, and generally makes life more enjoyable.

  3. Exercise has complex trade-offs.
    Consider whether exercise depletes willpower or builds good habits. Does it make you more confident or overconfident? The effects vary by individual.

  4. The quality of extra years matters.
    Are the extra years healthy, merely aged, or do they represent a slowing of the aging process? You are investing your best remaining years in health, so a downgrade in future year quality may be significant.

  5. Future technology could change the equation.
    If technological advances extend lifespans or improve quality of life (or even achieve escape velocity), then buying time now may be far more valuable.

  6. The subjective cost of time.
    If you hate exercising, its cost is strongly negative. Conversely, if you find an enjoyable form of exercise (perhaps by listening to podcasts or socializing), its cost may even be positive.

  7. Limited available time.
    We do not have 16 flexible, valuable hours each day. Fixed time costs (work, family, etc.) may make the opportunity cost of exercising higher.

  8. Risk of injury.
    Exercise can cause injuries—either directly or by depleting recovery time—which in turn may reduce the net benefit.

Understanding Exercise Engagement Challenges

Research and public discourse suggest that the primary barrier to exercise adoption may be more fundamental than previously considered. A notable perspective from social media provides insight:

Alternative Perspective on Exercise:
“The primary challenge with traditional exercise is engagement. Many find conventional workout routines monotonous, particularly strength training, which is often perceived as primarily aesthetic-focused. This suggests we should consider reframing physical activity around more naturally engaging forms of movement.

There may be value in exploring alternative approaches to physical activity that feel more intuitive and enjoyable. Activities like group sports or recreational games could provide similar health benefits while being more inherently engaging.

The fitness industry might benefit from examining how we can make physical activity more accessible and enjoyable, rather than focusing solely on traditional exercise methods.”

This perspective highlights an important consideration: while exercise has clear health benefits, its implementation needs to account for human psychology and motivation. Future approaches might benefit from incorporating more naturally engaging forms of physical activity that achieve similar health outcomes while being more sustainable for most individuals.

The Real Story Behind Inaction

The real reason many people do not exercise is, frankly, simple—and mostly a true story.
See here for more details.