Prevalence of Adverse Drug Reactions in Hospital Among Older Patients with and Without Dementia

Older inpatients with dementia are at an increased risk of an adverse drug reaction (ADR) during hospitalization.

To quantify the prevalence of ADRs in older inpatients according to dementia status and ADR definition approach and to identify risk factors of ADRs during hospitalization.

This was a retrospective cohort study of 2000 inpatients aged ≥ 75 years admitted consecutively to six Sydney hospitals (1 July 2016 to 31 May 2017). Dementia was defined by diagnosis in electronic medical records. ADRs were defined according to two approaches: the International Statistical Classification of Diseases and Related Health Problems, Tenth Revision, Australian Modification (ICD-10-AM) and classification by a research pharmacist (subset cohort, n = 600). A binary logistic regression was conducted to determine risk factors of ADRs.

Among 2000 patients, 25.9% (n = 517) were reported to have dementia. ADRs defined by ICD-10-AM were identified in 8.3% (n = 43) and 14.6% (n = 217) of inpatients with and without dementia respectively (p < 0.001). A total of 13.0% (n = 260) and 12.5% (n = 75) of patients had ADRs defined by ICD-10-AM and a research pharmacist, respectively. Key risk factors of ADRs were longer hospital stay [odds ratio (OR) 1.01, 95% confidence interval (CI) 1.01, 1.02) and a greater number of regular potentially inappropriate medicines (PIMs) on admission (OR 1.17, 95% CI 1.00, 1.38).

ADRs were more prevalent among inpatients without dementia and when assessed by a research pharmacist. Our findings underline the need for improved ADR detection in older inpatients.