The Relationship of Continuity of Care, Polypharmacy and Medication Appropriateness: A Systematic Review of Observational Studies

INTRODUCTION: Worldwide, polypharmacy and medication appropriateness-related outcomes (MARO) are growing public health concerns associated with potentially inappropriate prescribing, adverse health effects, and avoidable costs to health systems. Continuity of care (COC) is a cornerstone of high-quality care that has been shown to improve patient-relevant outcomes. However, the relationship between COC and polypharmacy/MARO has not been systematically explored. OBJECTIVE: The aim of this systematic review was to investigate the operationalization of COC, polypharmacy, and MARO as well as the relationship between COC and polypharmacy/MARO. METHODS: We performed a systematic literature search in PubMed, Embase, and CINAHL. Quantitative observational studies investigating the associations between COC and polypharmacy and/or COC and MARO by applying multivariate regression analysis techniques were eligible. Qualitative or experimental studies were not included. Information on the definition and operationalization of COC, polypharmacy, and MARO and reported associations was extracted. COC measures were assigned to the relational, informational, or management dimension of COC and further classified as objective standard, objective non-standard, or subjective. Risk of bias was assessed by using the NIH Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. RESULTS: Twenty-seven studies were included. Overall, substantial differences existed in terms of the COC dimensions and related COC measures. Relational COC was investigated in each study, while informational and management COC were only covered among three studies. The most frequent type of COC measure was objective non-standard (n = 16), followed by objective standard (n = 11) and subjective measures (n = 3). The majority of studies indicated that COC is strongly associated with both polypharmacy and MARO, such as potentially inappropriate medication (PIM), potentially inappropriate drug combination (PIDC), drug–drug interaction (DDI), adverse drug events (ADE), unnecessary drug use, duplicated medication, and overdose. More than half of the included studies (n = 15) had a low risk of bias, while five studies had an intermediate and seven studies a high risk of bias. CONCLUSIONS: Differences regarding the methodological quality of included studies as well as the heterogeneity in terms of the operationalization and measurement of COC, polypharmacy, and MARO need to be considered when interpreting the results. Yet, our findings suggest that optimizing COC may be helpful in reducing polypharmacy and MARO. Therefore, COC should be acknowledged as an important risk factor for polypharmacy and MARO, and the importance of COC should be considered when designing future interventions targeting these outcomes. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40266-023-01022-8.