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

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

Objective: 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.

Methods: 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.

Results: 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).

Conclusions: 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.