Demographics were age, sex, and race dichotomized into white versus nonwhite. Comorbid illness was quantified as the presence of 31 specific preexisting conditions, as recorded in the hospital’s administrative and billing database. We subdivided the 31 conditions into 2 groups. Group 1 comprises conditions that are predictive of poorer outcomes. Group 2 comprises comorbid conditions that have previously been associated with lower mortality; this association most likely represents the effect of coding bias, wherein milder chronic conditions are less likely to be coded for more severely ill patients. The 2 comorbid illness variables included in our models were the number of conditions present within each of these groups.