Development and validation of a prognostic index for 1-year mortality in older adults after hospitalization

Context For many elderly patients, an acute medical illness requiring hospi talization is followed by a progressive decline, resulting in high rates of mortality in this population during the year following discharge. However, few prognostic indices have focused on predicting posthospital mortality i n older adults. Objective To develop and validate a prognostic index for 1 year mortality o f older adults after hospital discharge using information readily available at discharge. Design Data analyses derived from 2 prospective studies with 1-year of foll ow-up, conducted in 1993 through 1997. Setting and Patients We developed the prognostic index in 1495 patients age d at least 70 years who were discharged from a general medical service at a tertiary care hospital (mean age, 81 years; 67% female) and validated it i n 1427 patients discharged from a separate community teaching hospital (mea n age, 79 years; 61 % female). Main Outcome Measure Prediction of 1-year mortality using risk factors such as demographic characteristics, activities of daily living (ADL) dependenc y, comorbid conditions, length of hospital stay, and laboratory measurement s. Results In the derivation cohort, 6 independent risk factors for mortality were identified and weighted using logistic regression: male sex (1 point); number of dependent ADLs at discharge (1-4 ADLs, 2 points; all 5 ADLs, 5 p oints); congestive heart failure (2 points); cancer (solitary, 3 points; me tastatic, 8 points); creatinine level higher than 3.0 mg/dL (265 mu mol/L) (2 points); and low albumin level (3.0-3.4 g/dL, 1 point; <3.0 g/dL. 2 poin ts). Several variables associated with 1-year mortality in bivariable analy ses, such as age and dementia, were not independently associated with morta lity after adjustment for functional status. We calculated risk scores for patients by adding the points of each independent risk factor present. In t he derivation cohort, 1-year mortality was 13% in the lowest-risk group (0- 1 point), 20% in the group with 2 or 3 points, 37% in the group with 4 to 6 points, and 68% in the highest-risk group (>6 points). in the validation c ohort, 1-year mortality was 4% in the lowest-risk group, 19% in the group w ith 2 or 3 points, 34% in the group with 4 to 6 points, and 64% in the high est-risk group. The area under the receiver operating characteristic curve for the point system was 0.75 in the derivation cohort and 0.79 in the vali dation cohort. Conclusions Our prognostic index, which used 6 risk factors known at discha rge and a simple additive point system to stratify medical patients 70 year s or older according to 1-year mortality after hospitalization, had good di scrimination and calibration and generalized well in an independent sample of patients at a different site. These characteristics suggest that our ind ex may be useful for clinical care and risk adjustment.