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

Abstract

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.

Fig. 1

PRISMA 2020 flow diagram. Reason 1: No quantitative association of COC and either polypharmacy or MARO investigated, reason 2: experimental design or review of interventional studies, reason 3: conference abstract (no full-text available), reason 4: language other than English or German. COC continuity of care, MARO medication appropriateness-related outcomes

Fig. 2

Association between COC and polypharmacy for objective standard COC measures. Solid green line indicates significant negative association between COC and polypharmacy; dashed red line indicates non-significant negative association; blue dotted line indicates significant positive association; [50] was not visualized, as results were not reported as OR, RR, or IRR; [54] uses low COC as the reference category. Therefore, an RR of 1.07 indicates a negative relationship between high COC and polypharmacy. *OR for care teams of PCPs only; **OR for care teams of specialists only; ***OR for care teams with both PCPs and specialists. COC continuity of care, COCI Continuity of Care Index (physician level), IRR incidence rate ratio, MARO medication appropriateness-related outcomes, OR odds ratio, PCP primary care physician/practitioner, RR risk ratio, SECON sequential continuity of care, UPC usual provider of care

Fig. 3

Association between COC and polypharmacy for objective non-standard and subjective COC measures. For [49], only the OR for 2 vs 1 physician among women was visualized. The association between the number of treating physicians and polypharmacy was significantly positive in all other subgroups. Solid green line indicates significant negative association between COC and polypharmacy. COC continuity of care, OR odds ratio

Fig. 4

Association between COC and MARO for objective standard COC measures. Solid green line indicates significant negative association between COC and MARO; dashed red line indicates non-significant negative association. [43] was not visualized, as results were not reported as OR, RR, or IRR. COC continuity of care, COCI Continuity of Care Index (physician level), DDI drug–drug interaction, HF heart failure, IRR incidence rate ratio, MARO medication appropriateness-related outcomes, OR odds ratio, PIM potentially inappropriate medication, RR risk ratio, SECON sequential continuity of care, UPC usual provider of care

Fig. 5

Association between COC and MARO for objective non-standard and subjective COC measures. Solid green line significant negative association between COC and MARO; red dashed line non-significant negative association. For [46], the OR for having 2 vs 1 prescriber was visualized (a significant negative association between COC and PIM was also found for 3 and 4+ vs 1 prescriber). For [49], only the OR for 2 vs 1 physician among women was visualized. The association between the number of treating physicians and polypharmacy was significantly positive in all other subgroups. For [56], the OR for 3–4 vs 1–2 prescribers was visualized (a significant negative association between COC and PIM was also found for 5 + vs 1–2 prescribers). For [69], only the longitudinal model was visualized. ADE adverse drug event, COC continuity of care, COCI Continuity of Care Index, DDI drug–drug interaction, MARO medication appropriateness-related outcomes, OR odds ratio, PIDC potential inappropriate drug combination, PIM potentially inappropriate medication