By Jules SADEFO KAMDEM

Population ageing and climate change jointly threaten the functional capacity that sustains autonomy, labour supply, productivity, and fiscal resilience. This paper develops a continuous- time, age-structured model in which healthy longevity is a regenerative form of human capital. Cohort health is exposed to biological depreciation, a standardised heat-stress state, diffusion risk, and marked compound-Poisson losses. Prevention, climate adaptation, education, and effectively accessible artificial intelligence can offset avoidable depreciation. AI is accumulated as a depreciating capital stock and requires complementary data, skills, inclusion, and organisational capacity. The paper derives a closed-form regenerative-prevention interval under a non-negativity constraint and gives correct piecewise comparative statics at the ero-prevention kink. Digital exclusion primarily reduces effective AI services and may additionally create a bounded substitution cost; it cannot generate an unbounded health loss. The model distinguishes absolute from logarithmic health inequality. It also endogenises post-retirement labour supply: AI can raise productivity, reduce task burden and fixed re-entry costs, and thereby enable voluntary re-employment of qualified retirees in flexible jobs. This produces an experience-retention channel through an average experience-quality spillover, in addition to the health, labour-productivity, and curative-spending dividends of prevention. Labour taxation and pension clawbacks affect hours and re-entry, so financing is distortionary rather than lump-sum. A reproducible common-random-number Monte Carlo calibration for 2025–2050 uses an AI-capital law, exact compound-Poisson counts, beta-distributed marks, no upper clipping of health, and diagnostics for numerical tails. Integrated prevention, adaptation, AI, inclusion, and flexible senior work deliver the largest social gains, although fiscal rankings remain ambiguous.

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