Multimorbidity measures were poor predictors of adverse events in patients aged ≥80 years: a prospective cohort study

To assess and compare the ability of two measures of multimorbidity and a simple disease count (DC) to predict health outcomes in a population of patients aged ≥80 years.A prospective, observational, and population-based cohort study including 567 individuals [3.0 years (standard deviation ± 0.25) follow-up].Of the patients, 37.6% were reported with five or more diseases. Multimorbidity was measured by means of a modified Charlson comorbidity index [mCCI; median score, 5 (range, 4-15)], Cumulative Illness Rating Scale [CIRS; median score, 4 (range, 1-11)], and a simple DC of 22 selected chronic conditions [median score, 4 (range, 0-13)]. All measures were independently related to mortality [adjusted hazard ratio (HR) mCCI, 2.5 (confidence interval {CI}: 1.5, 4.1); CIRS, 2.1 (CI: 1.4, 3.2); DC, 2.1 (CI: 1.4, 3.2)] and hospitalization [adjusted HR DC, 2.3 (CI: 1.7, 3.1); mCCI, 2.1 (CI: 1.5, 3.0), CIRS, 1.9 (CI: 1.5, 2.6)] but not to functional decline. Areas under the curve for mortality and hospitalization were all below 0.70. Net reclassification improvements did not indicate that any one measure provided a significant benefit over the others.In this population, the mCCI, CIRS, and unweighted DC predicted mortality and hospitalization but not functional decline. There is no clear advantage of using one measure over another.