Proportion of adverse events and number of patient frailty characteristics. Frailty characteristics associated with adverse events during hospitalization = cognitive impairment, anemia, recent unintentional weight loss, and any potentially inappropriate medication prior to admission. n= number of patients in each group. Significant test of trend, RS=0.25, p<0.001. Frailty characteristics associated with readmission within 30 days = hyponatremia, hospitalization within previous 30 days, and functional impairment. n= number of patients in each group. Significant test of trend, RS=0.31, p<0.001.