title: Why do estimates of the acute and chronic effects of air pollution on mortality differ?
abstract: Several investigators have discussed various reasons for the large and consistent difference in the relative risk estimates per unit exposure to air pollution derived from time-series and cohort study designs. This article considers whether the two study designs are estimating fundamentally different parameters even though both are commonly expressed in terms of relative risk coefficients. A frailty model for air pollution mortality is proposed to illustrate some of the theoretical behaviors of heterogeneous populations exposed to time-varying pollution patterns and their implications for the kinds of summary measures widely used in air pollution risk assessment.
authors: Department of Preventive Medicine, University of Southern California, Los Angeles, California, USA. dthomas@usc.edu
authors: Duncan
authors: D
authors: Thomas
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects; D000397:Air Pollution / Q000009:adverse effects*; D006801:Humans; D015233:Models, Statistical; D009026:Mortality; D013997:Time Factors
chemical_list: D000393:Air Pollutants