Mortality , Life Expectancy , and Daily Air Pollution for the Frail Elderly in Three U . S . Cities

Perhaps the clearest indications of adverse environmental health effects have been responses to short-term excursions in ambient air quality or temperature as deduced from time-series analyses of exposed populations. However, current analyses cannot characterize the prior health status of affected individuals. We used data on daily elderly death counts, ambient air quality indicators, and temperature in Philadelphia, Chicago, and Atlanta to estimate the daily numbers of frail elderly at-risk of premature mortality, their remaining life expectancies, and environmental effects on life expectancy. These unobserved frail populations at-risk were estimated using the Kalman filter. Frail life expectancies range from 13-16 days. Despite substantial differences in demography and environmental conditions in the three cities, frail life expectancies and contributions of ambient conditions are remarkably similar. The loss in frail life expectancy is approximately 12 hours. Conventional time-series analyses of air pollution effects report similar increases in daily mortality associated with air pollution, but our new model shows that such acute environmental risks are limited to a small fraction of the elderly population whose deaths were imminent in any event. This paradigm shift offered by the