Preventable and non-preventable risk factors for adverse drug events related to hospital admissions in the elderly - A prospective study

Objective: To ascertain preventable and non-preventable risk factors for adverse drug events (ADEs) in elderly inpatients at hospital admission. Patients and methods: This was a prospective study of 2814 inpatients over 70 years of age who were consecutively admitted from November 1997 to December 1999 to a 60-bed geriatric unit of a French university hospital, and the 500 consecutive ADEs that were present at admission. All drugs administered during the month preceding hospitalisation, signs or symptoms of ADEs, and risk factors related to the drug prescription or patient's diseases were considered: excess drug doses, potential drug-drug interactions (DDIs), interfering chronic disease and acute interfering disease. Results: 66.7% of the ADEs were associated with cardiovascular, metabolic, renal or neuropsychological symptoms. The drugs involved were mainly cardiovascular (43.7%) and psychotropic (31.2.%) drugs. One or more risk factors (mainly DDIs and/or interfering acute diseases) were recorded in 81.2% of ADEs. An interfering acute disorder (usually dehydration) was more frequent in ADEs resulting from drugs or drug combinations administered for 1 month or more (p < 0.05). 41.3% of risk factors were preventable (some DDIs, excess doses, interfering chronic diseases). One risk factor alone or the combination of all risk factors was preventable in 40.2% of ADEs. Conclusions: This study suggests that many ADEs in the elderly may be decreased by removing all the preventable risk factors before a drug is prescribed (mainly DDIs and excess doses) and by reinforcing drug monitoring when an interfering acute disease occurs.