Measuring health in aging is harder than it sounds
Everyone agrees that health must be measurable before aging can be treated. But agreeing on what health actually is turns out to be a scientific debate in its own right.
The World Health Organization introduced the concept of intrinsic capacity as a yardstick for healthy aging. It covers five domains: locomotion, cognition, sensory function, psychological wellbeing, and vitality. That final domain represents the body’s biological reserve, its ability to maintain internal balance under stress. Yet the article demonstrates that researchers rarely apply the concept in the same way.
The same word, dozens of definitions
Although the five domains are broadly accepted, their implementation varies enormously. Studies use different scoring methods, measurement instruments, and data sources, particularly for the vitality domain. This makes cross-study comparison unreliable. If a clinical trial on an anti-aging intervention uses a different definition of health than a comparable study, the results simply cannot be placed side by side.
This is not just an academic concern. As intrinsic capacity is increasingly used as an outcome measure in clinical trials within geroscience, the field that studies aging as a biological process, the lack of standardisation becomes a practical barrier to progress. Findings risk being misinterpreted or rendered incomparable.
An opportunity for geroscience
For the first time in human history, it may be possible to measure health directly, rather than inferring it from the presence or absence of disease. That is a meaningful shift. Age-related decline often begins years before any clinical diagnosis is made.
If intrinsic capacity can be measured reliably and consistently, it offers an early target for intervention. But that requires consensus on what is being measured and how. The authors call for clear, operationalisable definitions and rigorous measurement methods. The potential payoff is substantial: better comparability between studies, faster validation of effective interventions, and ultimately a stronger clinical framework for the aging body.
Search terms to explore further: intrinsic capacity WHO aging, geroscience outcome measures standardisation, vitality domain clinical aging research