Healthy Aging Index Construction

The index uses systolic blood pressure for the vascular system, fasting glucose for metabolic function, the Mini-Mental State Examination for cognition, serum creatinine for renal function, and forced vital capacity for pulmonary function. These were chosen because each represents a distinct physiologic system that declines with age and because all can be measured with routine, inexpensive methods. Together they capture aging as a multisystem process rather than the failure of any single organ, which is the central idea behind the index.

Each of the five markers is scored 0, 1, or 2 according to which risk category, typically a tertile, the individual falls into, with the least healthy category scoring 2. The five scores are summed without weighting to give a total from 0 to 10. A low score means most systems remain healthy, while a high score signals that many systems show subclinical decline at once. Higher scores are associated with greater mortality risk, so the total serves as a graded summary of multisystem biological aging.

The HAI is a five-marker physiologic composite focused on subclinical organ-system decline, scored 0 to 10. A deficit-accumulation frailty index counts many clinical deficits of any kind and expresses frailty as a proportion, while methods like the Klemera-Doubal estimator or epigenetic clocks produce a continuous biological age in years from biomarker or methylation data. The HAI is simpler and cheaper than biological-age algorithms and more physiologically specific than a broad frailty index. The measures correlate but capture different facets of aging and are often studied together.