Figure 9

Cross-validation by cause of death. Index coefficients were estimated based upon a training set of subjects that had died from one specific cause (cancer, cardiovascular, or non-cancer/non-cardiovascular). This generated a fitted model that was applied to a test set of subjects that had died from another specific cause, which differed from that of subjects in the training set. The discrimination ability of the model with respect to the survival times of subjects belonging to the test set was measured by estimating the concordance index (C). Train and test sets were either the n = 426 subjects that died of cancer, the n = 467 with cardiovascular-related deaths, or the n = 586 subjects with non-accidental deaths unrelated to cancer or cardiovascular disease. The dotted vertical line represents the estimated concordance index obtained for each cross-validation scenario. The density shown corresponds to a null distribution generated by 10,000 simulation trials. In these simulations, survival times in the training set were randomly permuted among subjects prior to estimation of model coefficients. The null distribution thus provides an indication of concordance values likely to arise by chance.