Intrinsic Capacity: The New Language of Healthspan

by Dr. Sean Cassleman, DO

For years, "healthspan" has been the word used to describe living not just longer, but better — more years free of disease and disability, not just more years on the calendar. It's a good concept, but it's always been a little abstract. A new term is starting to give it teeth: intrinsic capacity.

The New York Times recently introduced many readers to this idea in a piece by Dana G. Smith, "Intrinsic Capacity: The Most Important Longevity Term You've Never Heard Of" (August 2026). The article describes intrinsic capacity as a holistic measure of what a person's body and mind are actually capable of — not a single number on a lab report, but a composite picture built from cognition, mobility and strength, vision and hearing, psychological well-being, and vitality. First formalized by the World Health Organization in 2015, the framework represents a shift away from medicine that simply chases down and treats individual diseases, toward medicine that protects a person's functional ability to live their life.

That distinction matters more than it might sound. A patient can have "normal" bloodwork and a clean bill of health on paper, and still be losing the grip strength, balance, or stamina that let them live independently. Intrinsic capacity is designed to catch exactly that — the slow erosion of function that standard checkups often miss until it shows up as a fall, a hospitalization, or a loss of independence.

The science backs this up. A widely cited paper in the journal Age and Ageing, "Intrinsic Capacity and Healthy Ageing" by Chhetri, Harwood, Ma, Michel, and Chan (2022), lays out the five domains of intrinsic capacity — locomotion, sensory function, vitality, psychological health, and cognition — and makes the case that declines in these areas can show up well before a person is formally "disabled." The authors argue that tracking intrinsic capacity over time gives clinicians a way to intervene early, before small declines compound into serious, life-altering problems. That single idea — catch it early, before it becomes a crisis — is the whole philosophy behind how we practice medicine at Mission Metabolic Health.

Why This Is What We're All About

We built Mission Metabolic Health around a simple belief: our patients shouldn't just live long lives, they should be able to live those lives — fully, independently, and on their own terms, well into their later years. That means being able to travel, play with grandchildren, garden, climb stairs without thinking about it, and stay engaged with the people and activities that matter to them.

Getting there takes more than treating problems after they show up. It takes foresight. Our team combines metabolic testing, hormone and peptide optimization, and specialty exercise programming with concierge primary care specifically so we can see functional decline coming — and act on it — before it turns into a broken bone, a lost independence, or a hospital stay. When something does go wrong, the advantage isn't just that we treat it. It's that you already have a team in your corner who knows your history, coordinates your care, and stays with you through recovery so a single setback doesn't become a downward spiral.

A Patient's Story: Staying Ahead of Osteoporosis

One of our patients — we'll call her Jane, as we protect the privacy of the real women and men whose stories inform pieces like this — came to us in her early sixties with a osteoporosis diagnosis from a routine bone density scan. On paper, it was just a number. In practice, it was a warning sign for exactly the kind of decline intrinsic capacity is meant to catch: a loss of skeletal strength that, left unaddressed, raises the risk of a fracture that can cascade into lost mobility and lost independence.

Rather than simply noting the diagnosis and moving on, our team built a plan around her. She started a structured strength and resistance training program through our exercise physiology team, targeted specifically at building bone-loading strength and improving balance — the two factors most protective against fracture. We layered in mobility work to protect her joints and reduce fall risk, alongside nutritional and hormonal support tailored to her bone health. The goal wasn't just to manage a diagnosis; it was to actively rebuild the physical capacity that diagnosis put at risk.

Then, despite all of that preparation, she had a fall and suffered a minor wrist fracture. This is the moment that, in a lot of healthcare experiences, patients are left to navigate alone — bounced between an urgent care, an orthopedic referral, and a physical therapist who has never met them, with nobody coordinating the whole picture. That's not how it went for her.

Because she was already one of our patients, we got her in front of a trusted orthopedic specialist within our network immediately, with me coordinating her care from diagnosis through treatment. Once she was cleared for movement, our exercise team built an active recovery program to rebuild strength and range of motion without letting the rest of her conditioning lapse — and we used the moment to reassess and tighten up her fall-prevention plan, so we were actively working to prevent the next one, not just treating the one that happened.

That, in the end, is the real value of having a team like ours in your corner. It isn't just about reacting well when something goes wrong — though we do. It's about the preparation beforehand that lowers the odds something serious happens at all, the early detection that catches problems while they're still small, and the coordinated, guided care that carries you through when a challenge does arise, so it stays a minor setback instead of becoming a major one.

Measuring What Actually Matters

Intrinsic capacity is a useful new way to talk about healthspan because it puts the focus where it belongs: not on any single lab value, but on your actual ability to move, think, sense the world, and engage with life. That's precisely what we track, protect, and build at Mission Metabolic Health — not just adding years to your life, but making sure you have the strength, mobility, and resilience to use them fully.