A Method for Partitioning the Attributable Fraction of Multiple lime-Dependent Coexisting Risk Factors for an Adverse Health Outcome

Objectives. We decomposed the total effect of coexisting diseases on a timed occurrence of an adverse outcome into additive effects from individual diseases. Methods. In a cohort of older adults enrolled in the Precipitating Events Project in New Haven County, Connecticut, we assessed a longitudinal extension of the average attributable fraction method (LE-AAF) to estimate the additive and order-free contributions of multiple diseases to the timed occurrence of a health outcome, with right censoring, which may be useful when relationships among diseases are complex. We partitioned the contribution to death into additive LE-AAFs for multiple diseases. Results. The onset of heart failure and acute episodes of pneumonia during follow-up contributed the most to death, with the overall LE-AAFs equal to 13.0% and 12.1%, respectively. The contribution of preexisting diseases decreased over the years, with a trend of increasing contribution from new onset of diseases. Conclusions. LE-AAF can be useful for determining the additive and order-free contribution of individual time-varying diseases to a time-to-event outcome. (Am J Public Health. 2013;103:177-182. doi:10.2105/AJPH.2011.300458)