Our study findings suggest a modest increase in costs associated with an ADR-related hospitalisation and post-discharge compared to non-ADR hospitalisation with an average increase of €2050 per individual identified with an ADR. The majority of the differences in costs were attributed to the increases in nursing home care, increased accident and emergency department visits and hospital services after discharge for their acute episode in the ADR cohort. The average costs associated with ADRs were highest in those with possibly preventable ADRs and those with moderately severe or severe ADRs.
Comparison with other studies
There have been a small number of systematic reviews of studies examining the costs associated with ADRs or adverse drug events (ADEs) [6, 7] which is defined as ‘any injuries resulting from medication use, including physical harm, mental harm, or loss of function’.[17] The studies within these reviews are not focused specifically on the elderly and are conducted across different countries, settings and populations with different methodological approaches. In particular, a systematic review of thirty-one observational studies of ADEs found that the average “direct costs” in ambulatory care ranged from €702 to €40273, and average in-hospital costs from €943 to €7192.[6] There were significant methodological differences relating to the design, type of ADEs included and the type and structure of costs, but the costs remain higher across most studies. The studies were presented separately according to whether the ADE led to hospitalisation or occurred during hospitalisation. All ages were included and only one study in the review referred to indirect costs associated with ADEs leading to hospitalisation.[18] In this study the incremental cost per patient with an ADE was €1982. A German study included in the systematic review conducted a micro-costing study of ADEs using a retrospective and medical record–based study.[19] Those hospitalised for ADEs were matched to a non-ADE cohort with associated mean costs of €5113 and €4143 respectively (a difference of €970 ~ 23%). Another review examined observational studies to evaluate the economic impact of preventable ADRs and found the costs due to preventable ADRs in an inpatient setting had a wider range than outpatient setting: a minimum of €2851 to a maximum of €9015 in the inpatient setting compared to a minimum of €174 to a maximum of €8515 in the outpatient setting.[7]
One recent study in the UK found that the average costs associated with hospitalisation for medication harm (including ADRs) and healthcare utilisation after 8 weeks post-discharge was approximately £550.[20] Another study using the US Veterans Health Administration (VHA) database examined the costs of severe ADRs by drug-symptom pairs in 5113 outpatient ADR reports from 4880 veterans.[21] The authors were not able to report on total costs due to spontaneous reporting of ADRs. Of those pairs reported, reflecting more severe ADRs, the average costs were high ranging from US$9930 to US$49258. Another UK study extrapolated the costs of ADRs, based on a one month study period over which data on ADRs were captured, and applied this to national population figures.[22] A study in 2007 on the costs of emergency department (ED) visits related to ADRs for patients greater than 65 years of age using administrative data in Ontario, Canada found that ADR-related visits were $333 per ED visit and $7528 per hospitalization or an estimated $35.7 million in Canada.[23]
Strengths and Limitations – There are a number of strengths and limitations to our study. The strengths are the inclusion of screened ADRs in all those admitted to the tertiary centre and the comparison to a non-ADR population. Also, the detailed micro-costing data and follow-up of those admitted to hospital for 3 months after discharge to include other healthcare utilisation costs associated with the ADR hospitalisation.
However, there are a number of limitations. Comparisons with other studies are difficult due to differences in populations, definitions used, medications included, and cost sources. In addition, our study population were much older and, therefore, at higher risk of ADRs due to underlying comorbidities and polypharmacy. Also, the older aged populations are likely to be associated with other contributory factors such as complex medication regimens, cognition issues, vision deficits, nutrition, mobility/falls and fracture risk, social supports. The sample size in the ADR and non-ADR cohorts was relatively small, and only 66% of the ADR and non-ADR cohorts provided data at the 3-month follow-up. There are also limitations related to estimates of costs which are based on estimated time and units costs available.
ADR-related hospitalisation is a significant burden among the older aged population and often preventable. The costs associated with ADR-hospitalisation are modest, but also depend on the severity of the ADR. However, the cost is not only financial but is often associated with costs both clinically and personally for individuals. Early intervention, where possible, is important to avoid preventable medication harm. Intervention with more targeted policies to reduce ADRs through identification of those at highest risk and more awareness among HCPs and others involved in the care of the older populations will help to reduce costly hospitalisations and avoid increased morbidity and mortality.[24] A recent review of tools to help predict and detect ADR in older aged patients (≥ 60 years) identified eighteen studies using a variety of tools, but no one definitive and validated assessment tool for detecting and predicting ADR in elderly patients.[25] Therefore, more research is required to develop validated tools that can be implemented in clinical practice.[26–28] Empowering individuals and their care-givers through increased health literacy and education may help to reduce ADR-related hospitalisation and associated costs, and improving the transitions of care and pharmacy reviews are alternative interventions to help limit the impact of ADRs.[29]
In conclusion, ADR-related hospitalisation and post-discharge care in older individuals results in significant healthcare utilisation and costs. The costs are associated with preventability and severity of the ADR. More research is required to develop validated tools for prevention and early detection of ADRs that can be implemented in clinical practice to avoid unnecessary harm and burden, including economic burden.