Competing risks in absence of independence: Impact of AIDS on liver function failure mortality, and lung cancer on ischemic heart disease mortality

The increase in lung cancer (LC) mortality can produce a decrease in mortal ity from other causes, including ischemic heart disease (IHD). This problem (called the competing risks problem) has been addressed usually assuming i ndependence between the competing causes of death. Our purpose is to show t hat assuming dependence of causes of death allows obtaining a better estima tion of cumulative mortality. We use a clinical epidemiological example on the impact of AIDS in liver function failure in a cohort of drug users. The competing effect under dependence is 47% higher than under independence. T his result is compared with a population-based example on LC and IND mortal ities in Spanish people in 1992. LC and Ii-ID share tobacco smoking as a co mmon risk factor, so independence cannot be assumed. Under the independence assumption, bath life expectancy and number of deaths fr um IHD are undere stimated. The difference is small compared to the model computed under depe ndence and it occurs mainly in the elderly (0.3% more deaths in people aged 70 and over). (C) 2000 Elsevier Science Inc. All rights reserved.