Shaping human mortality patterns through intrinsic and extrinsic vitality processes

Human mortality patterns are modeled as the loss of an individual’s vitality, a measure of survival capacity, by senescence or when random extrinsic challenges exceed the remaining vitality. The model characterizes the stochastic rate of loss of vitality as a Wiener process and random extrinsic challenges as a Poisson process with exponentially distributed intensity. The model merges vitality and age-dependent mortally rate models into a framework that captures patterns of mortality from birth through senescence. The model provides a vitality-centric explanation for the increase in Swedish longevity over two centuries.