Healthspan vs Lifespan

The distinction

• Lifespan — total years lived, ending at death.
• Healthspan — years lived free of significant disease, disability, or functional impairment.

In high-income countries today, the gap between healthspan and lifespan is typically 8–12 years — people live with substantial chronic disease and functional limits for the last decade of life.

Compression of morbidity

James Fries (1980) proposed that the ideal trajectory is compression of morbidity: pushing the onset of chronic disease later, so that the period of disability shrinks even as lifespan grows. The opposite trajectory — expansion of morbidity — means living longer with more disability.

The geroscience case for treating aging is essentially: if aging biology is upstream of multiple diseases simultaneously, then slowing aging should produce compression of morbidity automatically.

Why the framing matters

• It changes what success looks like. A drug that extends lifespan without improving function is a worse outcome than one that extends healthspan even modestly.
• It informs trial endpoint design (composite morbidity-free survival rather than mortality alone).
• It changes individual decision-making: optimise for being functional at 85, not for hitting 100 in a bed.

Measurement

• Disability-free life expectancy (DALY-adjusted).
• Composite morbidity-free survival.
• WHO healthspan metrics.

Related entries

Centenarians, Frailty, Geroscience hypothesis, TAME trial.