Background Drug–drug interactions (DDIs) can lead to medication-related harm, and the older population is at greatest risk. We conducted a systematic review and meta-analysis to estimate DDI prevalence and identify common DDIs in older community-dwelling adults. Methods PubMed and EMBASE were searched for observational studies published between 01/01/2010 and 10/05/2021 reporting DDI prevalence in community-dwelling individuals aged ≥ 65 years. Nursing home and inpatient hospital studies were excluded. Study quality was assessed using the Joanna Briggs Institute critical appraisal tool. Meta-analysis was performed using a random-effects model with logit transformation. Heterogeneity was evaluated using Cochran’s Q and I². DDI prevalence and 95% confidence intervals (CIs) are presented. All analyses were performed in R (version 4.1.2). Results There were 5144 unique articles identified. Thirty-three studies involving 17,011,291 community-dwelling individuals aged ≥ 65 years met inclusion criteria. Thirty-one studies reported DDI prevalence at the study-participant level, estimates ranged from 0.8% to 90.6%. The pooled DDI prevalence was 28.8% (95% CI 19.3–40.7), with significant heterogeneity (p < 0.10; I² = 100%; tau² = 2.13) largely explained by the different DDI identification methods. Therefore, 26 studies were qualitatively synthesised and seven studies were eligible for separate meta-analyses. In a meta-analysis of three studies (N = 1122) using Micromedex^®, pooled DDI prevalence was 57.8% (95% CI 52.2–63.2; I² = 69.6%, p < 0.01). In a meta-analysis of two studies (N = 809,113) using Lexi-Interact^®, pooled DDI prevalence was 30.3% (95% CI 30.2–30.4; I² = 6.8%). In a meta-analysis of two studies (N = 947) using the 2015 American Geriatrics Society Beers criteria^®, pooled DDI prevalence was 16.6% (95% CI 5.6–40.2; I² = 97.5%, p < 0.01). Common DDIs frequently involved cardiovascular drugs, including ACE inhibitor-potassium-sparing diuretic; amiodarone-digoxin; and amiodarone-warfarin. Conclusions DDIs are prevalent among older community-dwelling individuals; however, the methodology used to estimate these events varies considerably. A standardised methodology is needed to allow meaningful measurement and comparison of DDI prevalence.

Background Older adults in Ireland are at increased risk of adverse drug events (ADE) due, in part, to increasing rates of polypharmacy. Interventions to reduce ADE in community dwelling older adults (CDOA) have had limited success, therefore, new approaches are required. A realist review uses a different lens to examine why and how interventions were supposed to work rather than if, they worked. A rapid realist review (RRR) is a more focused and accelerated version. The aim of this RRR is to identify and examine the contexts and mechanisms that play a role in the outcomes relevant to reducing ADE in CDOA in the GP setting that could inform the development of interventions in Ireland. Methods Six candidate theories (CT) were developed, based on knowledge of the field and recent literature, in relation to how interventions are expected to work. These formed the search strategy. Eighty full texts from 633 abstracts were reviewed, of which 27 were included. Snowballing added a further five articles, relevant policy documents increased the total number to 45. Data were extracted relevant to the theories under iteratively developed sub-themes using NVivo software. Results Of the six theories, three theories, relating to GP engagement in interventions, relevance of health policy documents for older adults, and shared decision-making, provided data to guide future interventions to reduce ADEs for CDOA in an Irish setting. There was insufficient data for two theories, a third was rejected as existing barriers in the Irish setting made it impractical to use. Conclusions To improve the success of Irish GP based interventions to reduce ADEs for CDOA, interventions must be relevant and easily applied in practice, supported by national policy and be adequately resourced. Future research is required to test our theories within a newly developed intervention.