AbstractBackgroundAdverse events are any injuries caused by healthcare management, which result in disability, increased length of stay or death. The Irish National Adverse Event Study (INAES)(1) used the Harvard Medical Practice, 2-step methodology of retrospective chart review(2) to determine the adverse event rate in the Irish inpatient cohort.MethodsWe further analysed the INAES data in order to calculate the prevalence and determine the impact of adverse events on the older inpatient population.ResultsINAES captured 1574 randomly selected adult inpatient admissions from 8 hospitals across the Republic of Ireland in 2009. 53% were female and the median age was 55years (IQR 37years to 72years). The prevalence of adverse events was higher in those aged >=65 compared to those aged < 65 (15.4% versus 9.3% P < 0.001). When an adverse event did occur it was more likely to result in death in the >=65 years old group (11.4% versus 2.1%, p = 0.01). Furthermore, it was 9 times more likely that an admission would result in a fatal adverse event in those aged >=65 compared to those aged < 65 years. A further 9% of adverse events in the >=65 age group resulted in permanent disability and over half were thought to be preventable. Older patients who suffered from an adverse event had an increased length of stay compared to older patients who did not suffer an adverse event (16days versus 6days, p <0.001) at a cost of EUR9,090 for each adverse-event-associated admission.ConclusionOlder inpatients are more likely to suffer from an adverse event than their younger counterparts. These adverse events are more likely to contribute to increased morbidity but over half are preventable. The follow-up INAES-2 study, which is currently underway, will determine if an improvement has been made after implementation of the National Clinical Programmes.