The biological scaffolding for the argument comes from the concept of homeodynamic space, developed over years of work in biogerontology. Rather than envisioning health as a fixed state of perfection, homeodynamic space describes the buffering capacity of a biological system—its reserve to withstand stressors and maintain stability. Ageing, in this framework, is the gradual contraction of that space, and health in later life is best understood not as the absence of any deviation from youthful reference values but as homeodynamic space remaining large enough to support adequate, rather than perfect, independence. The word “adequate” is doing the conceptual heavy lifting here. It shifts the definition of health away from a perfectionist ideal and toward a threshold that is personally meaningful and socially negotiated, leaving explicit room for the question of who is doing the defining.

That question has become newly urgent in the field. A recent systematic review of the healthspan literature identified 187 distinct definitions across 207 eligible studies, a divergence its authors read as evidence that no single biomedical criterion has settled the matter. Other prominent voices in geroscience have asked whether healthspan is even a coherent scientific construct, or simply a convenient label for something that is, in practice, negotiated rather than measured. Hernández-Pando’s contribution is to bring these threads together—and then to ground them in the messy reality of a single, fragmented, and unequal health system, using Mexico as the case study. Mexico is not chosen because its situation is unique, he stresses, but because its scale and its sharp socioeconomic gradient make the gap between optimal and adequate unusually visible: the country counted 32 million people aged 50 and older in 2024, with chronic disease the norm rather than the exception.

The distinction between the two standards has deep roots. In the 1970s, the medical sociologist Aaron Antonovsky proposed replacing the question that has organized most of modern medicine—what causes disease—with a “salutogenic” question: what generates and sustains health despite constant exposure to stressors. Antonovsky placed every person on a single ease–dis-ease continuum rather than sorting them into separate healthy and sick categories, and argued that movement along that continuum depends less on the absence of pathology than on a sense of coherence, the felt sense that one’s life is comprehensible, manageable, and meaningful. Empirical work applying the salutogenic model to older adults has found that a stronger sense of coherence predicts better subjective health independently of how much disease a person carries. Salutogenesis, Hernández-Pando notes, was asking the homeodynamic question decades before biogerontology gave it a biological vocabulary.

Modern geriatric medicine has independently converged on the same separation of standards. The Patient Priorities Care framework developed by Tinetti and colleagues for older adults with multiple chronic conditions distinguishes disease-guided care, where each condition is managed against its own guideline target, from patient-priority-directed care, organized around the outcomes that matter most to the individual—even when that means tolerating biomarker values that fall short of a disease-specific optimum. Critically, clinical trials have shown that aligning care with patients’ own priorities reduces treatment burden without worsening the outcomes patients themselves value. The World Health Organization’s healthy ageing framework offers a population-level version of the same idea, defining health as the ongoing process of maintaining the functional ability that lets a person be and do what they have reason to value, produced by the interaction between intrinsic capacity and environment. There is even hard evidence that attitude, not biology alone, shapes adequacy: in a study following the same individuals for up to twenty-three years, people with more positive self-perceptions of their own ageing lived on average 7.5 years longer than those with more negative self-perceptions, an advantage that persisted after controlling for age, sex, and functional health.

Against this conceptual backdrop, the Mexican data illustrate why the gap between standards is not merely philosophical. Hypertension affects 43.3 percent of Mexicans aged 53 and older, diabetes 25.6 percent, and multimorbidity is the rule. Frailty affects close to 8 percent of community-dwelling older Mexicans, and social frailty independently predicts mortality over nine years of follow-up. Meanwhile, the resources to manage this burden are severely fragmented: contributory institutions cover formal sector workers while a parallel program serves roughly 70 million people outside formal employment with less than half the per-person resources. Out-of-pocket spending has climbed to nearly 39 percent of total health expenditure, and 37.9 percent of Mexicans aged 65 and older lived in poverty in 2020. Even the diagnostic thresholds for conditions like sarcopenia, long imported wholesale from European and American cohorts, are only now being replaced with locally derived reference values.

The consequences of ignoring the adequacy standard are concrete and measurable. In older adults, the hospital itself is a risk factor: roughly one in three patients older than 70 leaves the hospital less able to perform basic activities of daily living than when they arrived, a phenomenon well documented enough to have its own name, hospitalization-associated disability. Avoidable hospitalizations for type 2 diabetes and hypertension among Mexicans without social security are concentrated, not randomly, in the country’s most marginalized municipalities—tying the fragmented insurance landscape directly to clinical outcomes. And the problem is global: catastrophic out-of-pocket health spending pushed roughly 2 billion people worldwide into or further into poverty in 2019 alone.

What makes the perspective striking is that Hernández-Pando is not primarily asking for more—more technology, more specialists, more budget. Those calls are not wrong, he writes, but they leave untouched a second lever that costs nothing to build because it already exists: the more rational, patient-centered use of resources a health system already has. Minimally disruptive medicine, developed for patients with multiple chronic conditions, asks what combination of treatments imposes the smallest burden on a person’s actual capacity, time, and finances while still advancing that person’s goals. On the delivery side, Comprehensive Geriatric Assessment—a structured but replicable way of asking the right questions about mobility, cognition, mood, medication, and social support, delivered to frail, community-dwelling older people rather than reserved for those already in a hospital bed—reduced the risk of unplanned hospital admission by roughly one sixth across a systematic review of twenty-one trials and nearly 7,900 participants. Combined, these amount to a screening and decision layer, deliverable by trained community health workers as well as physicians, that treats functionality, which biomarkers accompany rather than replace, as the outcome the whole system exists to protect.

The author even sketches how a patient-based measure of adequate health could be built from instruments that already exist, requiring no new tools. Functional activity is already captured by Fried’s frailty phenotype and its brief self-report derivative, the FRAIL scale—a five-question interview any clinician or community health worker can score without equipment. Social context can be approximated with the brief social-support screen built into the WHO’s ICOPE pathway, and attitude toward one’s own ageing with a short sense-of-coherence instrument in Antonovsky’s tradition. What would be new is administering these routinely, at every visit rather than once, and reading the trend rather than the single score—notably because Mexican longitudinal data show older adults are more likely to improve from frail or prefrail states than to worsen, unsettling the reflex of treating decline as simply what ageing looks like. Underlying the whole argument is a matter of distributive justice: with the WHO finding that roughly one in two people worldwide hold ageist attitudes, and the WHO’s own healthy-ageing language drawn from Amartya Sen’s capability approach, adequate health is framed not as a lesser standard than optimal health but as what a health system fairly owes every person—a chance to convert whatever resources exist into the life that person has reason to value.