LIMITS TO HUMAN LIFE EXPECTANCY - EVIDENCE, PROSPECTS, AND IMPLICATIONS

Identifying limits to human life expectancy and life span is difficult because survival is determined by the individual's physiology, exogenous influences, and their interaction over time. To explore theoretical limits, the authors examine the life expectancy of selected populations with good health behavior and apply a multivariate risk-factor model to longitudinal data. The risk-factor model and the population data produce consistent estimates of a lower bound of the theoretical limit to human life expectancy. The results suggest that such limits may be higher than estimates obtained by extrapolating human mortality trends, which, necessarily, are dependent on historical conditions. The investigation emphasizes the need to use information on individual physiological processes and health changes prior to death, in addition to mortality or "endpoint" data, in making estimates. Doing so can help, for example, to determine whether current conditions are stable or in flux.