Is Age an Independent Risk Factor of Adverse Drug Reactions in Hospitalized Medical Patients?*

OBJECTIVE: To study the incidence and the risk factors of adverse drug reactions. DESIGN: Multicenter survey. SETTING: Hospitalized care: 22 internal medicine and 19 geriatric wards. PATIENTS: All patients (n = 9,148) consecutively admitted during two observation periods of 2 months. MAIN OUTCOME MEASURE: Incidence of adverse drug reactions. RESULTS: The mean age was 67.1 +/- 0.17 years (median 72); the mean duration of hospital stay was 18.1 +/- 0.19 days (median 14). Each patient was administered 5.1 +/- 0.03 (median 5) drug prescriptions. The incidence of probable or definite adverse drug reactions was 5.8% (532/9,148). In univariate analysis, the incidence of adverse drug reactions increased from 3.3% at under age 50 to 6.5% at age 70-79 and decreased over age 80 (5.8%). In multivariate logistic regression, taking more than four drugs (OR = 2.94, CI = 2.38-3.62), staying in hospital more than 14 days (OR = 2.82, CI = 2.26-3.52), having more than 4 active medical problems (OR = 1.78, CI = 1.29-2.45), staying in a medical ward instead of geriatric ward (OR = 1.33, CI = 1.09-1.63), and drinking alcohol (OR = 1.28, CI = 1.03-1.58) were positively correlated with adverse drug reactions occurrence (P less than 0.05). Age, gender, and smoking cigarettes were not significant predictors of adverse drug reactions. CONCLUSION: Age is not an independent risk factor of adverse drug reactions, and good geriatric care can reduce the incidence of adverse drug reactions.