A trustful relation between the citizen and the healthcare professional enhanced the citizen's motivation and engagement in health-related preventive interventions, thus a trustful relation can be a prerequisite for preventing avoidable hospitalizations.

A trustful relation was established through specific actions, including solving practical issues, availability of care and responsiveness to the individual needs (59, 60, 62, 63). These actions gave rise to continuous contacts between the healthcare professional and the citizen, and thereby contributed to a trustful relation. Healthcare professionals providing home care can prevent avoidable hospitalizations, e.g., nurse practitioners in long-term care settings (60) and multidisciplinary teams providing home care to elderly citizens who prefer to stay in their own home and community (62). Trustful relations were built by providing practical advice and solving important practical issues that were not directly health-related (60, 62), such as installing loft insulation in the home (62). In addition, trustful relations were built through the availability of care and responsiveness to individual care needs, e.g., by spending extra time for the initial assessment, by providing more time for patient care, by having sufficient in-depth knowledge to deliver targeted information and emotional support, by ensuring continuity of care, and by emphasizing the personal relation (59, 60, 62, 63).

A thorough initial assessment enabled some patients to stay at home. It also provided them with an integrated care package, involving comprehensive care delivered by a team of nurse practitioners, specialist nurses, healthcare assistants, and care coordinators (62). More patient care helped older people regain their independence, which was seen as a key feature of intermediate care, involving individual care plan, a planned outcome, time-limited care, and cross-professional working (59, 63). Many patients favored the intermediate care services over hospital environments, appreciated the homely atmosphere and the locality of facilities, and felt that healthcare professionals had more time for patient care (63).

From the healthcare professionals' perspectives, having in-depth knowledge of the older people at long-term care homes and the ones living at home to meet their individual care needs was important to prevent avoidable hospitalizations (60, 62). From a nurse practitioner perspective, an important aspect of providing person-centered care was to notice subtle changes in health status, which required intimate knowledge of often complex health conditions, when descriptions focused primarily on health status (60). Then it was possible to meet the resident's need for informational and emotional support by keeping the resident (and family) informed about changes in health status or medication (60).

The continuity of care and the personal relation between older residents living at home and their healthcare professionals were important components in preventing avoidable hospitalizations. For example when patient's healthcare needs was pre-emptied the weekend (62); and through long-standing relationship between patient and general practitioner (40, 42, 52). Among people with diabetes, the optimal (maximum) time interval between general practitioner visits was 9–13 months for people with no diabetes complications, 5–11 months for people with 1–2 diabetes complications, and 4–9 months for people with 3+ diabetes complications if the visits were to protect against avoidable hospitalizations (42).

Multidisciplinary and cross-sectoral teamwork was established to meet complex care needs and to prevent avoidable hospitalizations, yet evidence on multidisciplinary care efforts was inconsistent. Nevertheless, good interdisciplinary collaboration between the healthcare professionals can enhance care coordination.

Multidisciplinary teams were established to overcome fragmentation and deliver better health outcomes for people with chronic diseases. However, there is mixed evidence on the effectiveness of multidisciplinary team-based practices, both across primary care institutions (45, 50, 57), and across primary and secondary care (6, 47–49, 56). A multidisciplinary team case management intervention, involving regular review and monitoring combined with an individual care plan for older people with ACSCs, had limited effect on reducing avoidable hospitalizations (48). Further, citizens with diabetes who received care managed by a physician outside of a primary care network were more likely to be hospitalized with ACSCs compared to citizens with diabetes who received care coordinated by a physician within the primary care network together with other healthcare professionals, but the differences between the two groups were small (56). Meanwhile, positive results were found in a multidisciplinary diabetes service on reducing avoidable hospitalizations when the multidisciplinary team comprised an endocrinologist, advanced-skilled general practitioners, a credentialed diabetes educator, and a podiatrist (50). Further, assigning a dedicated general practitioner to a nursing home was effective in preventing avoidable hospitalizations; this was explained by more efficient communication between the nurses at the nursing homes and the general practitioners (49).

From the healthcare professionals' perspectives, good interdisciplinary collaboration could enhance care coordination (60, 62), involving good working relationships between community-based healthcare teams and other services, such as outpatient clinics specializing in falls, general practitioner surgeries, and local councils enhanced care coordination (62).

Clear roles and clear responsibilities were important to provide coordinated care and to prevent avoidable hospitalizations when multiple healthcare professionals were involved and when services were constituted in home, municipality and hospital settings (59–63). For example, care plans that were left in the patient's home were difficult to keep up to date, which challenged the care coordination, when several healthcare professionals were involved (62). Confusion regarding the roles and responsibilities in multidisciplinary care work posed a risk for avoidable hospitalizations (59, 63). Consensus should be reached on the roles and responsibilities in the multidisciplinary teamwork, e.g., through discussions on when and where the care work needs to be done, and by whom (59). For example, team-based interventions outlining the healthcare professionals' preliminary roles and responsibilities in the care efforts were found to reduce avoidable hospitalizations (47, 51). In intermediate care facilities, where the care work was performed across settings such as hospital, general practice, nursing home, and residential home settings, a variety of prescribing arrangements in the distinct care settings resulted in confusion regarding prescribing responsibilities, thus posing a risk for patient safety and avoidable hospitalizations (63). To overcome confusion regarding roles and responsibilities in the provision of integrated care services across health disciplines and health institutions, it was beneficial and fostered coordination of care when a healthcare professional or administrative staff with a coordinating function had the overall responsibility for organizing the work (60, 61).

A focus on treatment in the healthcare system dominated preventive practices. Consequently, preventive services were underused. Financial incentives to general practitioners were provided to promote interventions targeted avoidable hospitalization.

Preventive interventions were established in the interface between primary and secondary care settings, as alternatives to hospital-based care (e.g., intermediate care institutions and emergency beds) (46, 63). Increasing emergency bed capacity within the primary care sector was found to reduce avoidable hospitalizations related to asthma, angina, and chronic obstructive pulmonary disease (46). Further, intermediate care was introduced as a facility organizationally located between primary and secondary care, across which medicines have to be managed (59, 63). The care practices performed across primary and secondary care brought a shift in the responsibility for the care practices between the healthcare professionals, but also between the healthcare professionals and the citizen. In intermediate care settings, the patients expected the healthcare staff to take control of their medicine as being in a healthcare facility, while the healthcare professionals found that they needed to be in control of the patients' medicines to ensure patient safety (63). Self-management interventions targeted people with chronic disorders showed no effect on avoidable hospitalizations (6, 44). Rather, the increased focus on high-risk patients resulted in the diagnosis of additional conditions requiring hospitalization (6), and a longer intervention period was necessary to reveal positive results (44).

The division between treatment and preventive care entails difficulties in the implementation of interventions targeting the prevention of avoidable hospitalizations (59, 63). From the perspective of healthcare staff in intermediate care settings, the preventive services were underused as focus was on reducing acute care pressures, and little awareness and understanding of intermediate care was seen among hospital staff (59). A key barrier for using preventive services was difficulties with referring to intermediate care, which made practitioners revert to specialized healthcare services (59).

Financial incentives, such as payment and compensation schemes, supported the recruitment of general practitioners to participate in preventive interventions and draw their focus to specific conditions deemed avoidable (41, 55, 61). General practitioners perceived such incentives as a recognition that additional work needed to be done (61). Financial rewards for preventing avoidable hospitalizations were especially effective for conditions selected as attention points by the healthcare authorities (41). Citizens with diabetes listed at a general practice receiving a higher share of payments through compensation schemes were less likely to experience avoidable hospitalizations (55).

Tailored tools to guide and support healthcare professionals in primary care could prevent avoidable hospitalizations, as these tools motivated to initiate initiatives by drawing their attention to specific conditions deemed avoidable.

Clinical decision-making tools and web-based IT platforms were provided to general practitioners, which was found supportive to identify patients at high risk of avoidable hospitalizations, and thus facilitated the initiation of targeted preventive services (53, 54, 61). A fast-track consultation providing general practitioners with a direct phone line to hospital-based specialists played a role in the management of patients' treatment plans and in the prevention of avoidable hospitalizations (54). Also a triage tool that helped determine whether people with uncomplicated rectal bleeding needed to be hospitalized (53), and web-based tools providing focused and simple systems with direct access to relevant clinical information about residents (53, 54, 61) were found to prevent avoidable hospitalizations. General practitioners found that intuitive systems, which summarized relevant clinical information and allowed for recording of review decisions, were supportive in their clinical decision-making on whether and when to follow-up patients (61). General practitioners valued the focused data presentation and case-finding ability, as these features could help identify historical risk factors, which they were likely to overlook when using the usual medical record (61).

Informational and educational material, such as prescribing advice, structured written educational material, educational outreach visits, and tailored newsletters motivated healthcare professionals to engage in preventive interventions (61). Educational training and clinical decision support was shown to prevent avoidable hospitalizations in an intervention that included physician training and continuing education, physician participation in disease management programs, data-driven quality improvement, and computerized decision support (43, 58). General practitioners and primary healthcare professionals involved in preventive work and quality improvement, were motivated to engage in preventive interventions when the information material highlighted that the preventive care practices was about patient safety (61). These safety issues resonated with messages received from other sources; this provided high legitimation of the intervention and the implied actions, which motivated healthcare professionals facilitated to engage in an preventive intervention focusing on medicines prescribing in their clinical practices (61).

This integrated finding was generated from two categories: category (1) a trustful relation between the citizen and healthcare professionals is a prerequisite for preventing hospitalizations, and category (2) multidisciplinary and cross-sectoral teamwork is established to prevent avoidable hospitalizations. This synthesis emphasizes the importance of continuity of care, including a trustful relation between citizen and healthcare professional, as a driver of care coordination, and thereby providing interventions that adapts to individual needs to prevent avoidable hospitalization. A history of interaction with the same general practitioner was shown to prevent avoidable hospitalizations (40, 42, 52), which highlights the potential of structured and person-centered care plans conforming to individual needs (including both health-related and practical issues) to prevent avoidable hospitalizations (59, 60, 62, 63). Other studies have shown that the risk of hospitalization is affected by disorder-related factors, including progression of disease, multimorbidity, mental-physical comorbidity (67–70), by person-related factors, including delayed health seeking, lack of knowledge, awareness and understanding of condition, perceived stress, low income, education and self-care abilities (67, 71–75), and by system-related factors, including service capacity, lack of care continuity, and little coordination between healthcare sites (75, 76). This is in line with the WHO framework on integrated people-centered health services (17), which conceptualizes care continuity as a complex concept of four domains: (1) interpersonal, (2) longitudinal, (3) management, and (4) informational continuity. The WHO framework recognizes overlaps between care continuity and coordination, where continuity enables effective care coordination that adapts to individual needs to ensure that the care is integrated and person-centered across various care settings. Likewise, our review findings showed that assigning a dedicated general practitioner in a nursing home was effective in reducing preventable hospitalizations, and this was explained by more efficient communication between nurses at the nursing homes and general practitioners (49). Thus, preventive interventions should not only address the direct health-related issues; such interventions should also consider the citizen and the context, including this individual's living conditions and needs for support, to prevent avoidable hospitalizations.

This systematic review excluded studies on palliative care interventions and findings representing the perspectives of relatives. This was done to focus explicitly on citizens at risk of avoidable hospitalizations and the healthcare professionals involved in interventions aiming to prevent avoidable hospitalizations. Supplementing our review findings, another mixed methods systematic review (77) focused on palliative care patients and their families. This study reports on the experiences of patients and their families, highlighting their needs of developing continuous relationships with clinicians (relational continuity) and coordinated, comprehensive information sharing within a range of services or professionals (informational continuity). The review stated a reduction in avoidable hospital admissions owing to interventions designed to promote informational and relational continuity (77). Further, a lack of informational and relational continuity negatively impacted the experiences of people with palliative care needs and their families, who had to act as a coordinator between the person with care needs and the healthcare professionals (77). Another study showed that older people valued good communication and a confidential and caring relationship with their primary care provider, as it facilitated their involvement in own care (78).

The present review findings are based on interventions targeting different groups, e.g., older people and people with chronic disorders, with seemingly various care needs; older people might have more complex needs as they are likely to be more cognitively or physically impaired because of their age, whereas people with diabetes without complications might have more direct needs. Yet, despite these potential differences in care needs, the review highlights the importance of care continuity, including a trustful relation between the citizen and healthcare professional. Accordingly, a study showed that consulting a primary care provider who was known and trusted was important to 62.6% of the respondents (79). Thus, care continuity can be underscored as an important component to prevent avoidable hospitalizations. This is also supported by the practice priorities put forward in the WHO framework (17), which aims to guide practitioners, providers, organizations, and system leaders to organize, manage, and deliver care that best meets citizen's health needs.

Further, this synthesis of evidence emphasizes the importance of clarifying the roles and responsibilities in team-based interventions to foster continuity and coordination of care. The results revealed underlying misunderstandings of other healthcare professionals' roles, and confusion regarding the division of responsibilities in multidisciplinary efforts, which may pose a patient safety risk. Team-based interventions fostered continuity and coordination of care when a healthcare professional or administrative staff with a coordinating function had the overall responsibility for organizing the work (60, 61). Another study showed that healthcare professionals were less motivated to participate in integrated care when the specific roles and responsibilities were unclear in the interdisciplinary team, implying a need for shared responsibility to engage all healthcare professionals (80). To build coordinated care practices, the roles and responsibilities should be outlined prior to initiation of the collaboration, for example through discussions of when and where the care work should be done, and by whom.

Fifteen of the 25 included articles provided evidence on multidisciplinary and cross-sectoral teamwork to prevent hospitalization (7, 45, 46, 48–52, 57, 58, 60–63, 67). The studies revealed inconsistent results for the prevention of avoidable hospitalizations, with fewer avoidable hospitalizations related to diabetes and limited effect among older people with ACSCs. A possible explanation could be that different types of coordination and collaboration between healthcare professionals is needed, depending on whether the person have complex care needs requiring involvement of different healthcare specialists, or more simple care needs (e.g., uncomplicated diabetes) for which healthcare and actions have been further developed and targeted (81). Nevertheless, the fragmentation of care practices, i.e., provision of care in various settings, combined with the involvement of different healthcare professionals remain barriers for ensuring continuous care and coordinated care practices.

The second integrated finding was generated from category 3) Integration of preventive interventions in healthcare services prevent avoidable hospitalizations, and category 4) Targeted tools guide and support primary healthcare professionals in initiating preventive interventions. This synthesis reveals that the sectoral divisions between primary and secondary care manifest in a demarcation between prevention and treatment, which influences the care practices aiming to prevent avoidable hospitalizations. To motivate and engage healthcare professionals in preventive interventions, financial incentives and supportive tools are provided to help stimulate especially primary care professionals in addressing avoidable hospitalizations. Correspondingly, the WHO framework (17) highlights financial incentives, technology, and education as enablers of care coordination that enhance the management and the informational continuity of care. The WHO framework recognizes that financial incentives aligned with shared outcomes of specific care practices are important components to provide more comprehensive care along the entire care pathway (17). In addition, review findings have contributed with evidence on the effects of financial incentives (41, 55, 61), clinical decision-making tools for general practitioners, and support systems for clinical recording and patient reviews, which were all shown to prevent avoidable hospitalizations (53, 54, 61). Thus, to successfully engage healthcare professionals in preventive care efforts, intervention components should comprise financial incentives, branding of interventions, and information and educational material. These components have been shown to enhance the healthcare professionals' engagement, to bring their professional knowledge and values into play (e.g., increased patient safety or implied preventive actions), and to make the intervention ethically legitimate from a professional point of view. One excluded study, which did not meet the inclusion criteria as it evaluated the cost-effectiveness of a primary care program aimed at preventing avoidable hospitalizations (82). In this program, general practitioners were invited to manage patients while using any resources required up to a cost of approximately $266 per patient; the results showed that 104 patients of the 707 enrolled patients were admitted to hospital (82). Such primary care programs are supported by the WHO, which highlights the primary care sector as a central player in coordinating health services across various disciplines and organizational boundaries (7, 17). Based on our results, and in line with other studies (7, 83, 84), it can be concluded that a fragmented healthcare system tends to result in suboptimal care and poor quality of care, which may impose a risk for patient safety and avoidable hospitalizations. Consequently, prevention should form an integral part of the care provided to truly engage and motivate healthcare professionals in preventive care. Moreover, the preventive efforts should account for the citizens' individual needs, and this should be reflected in relevant educational material, in financial incentives, and at platforms for sharing information across healthcare settings.

In this review, studies on readmissions were excluded to correspond to the distinction between hospital admissions and readmissions applied in existing research articles on avoidable hospitalizations, but this operationalization might not be meaningful in practice as admissions and readmissions occur on a continuum. Supplementing our review results, a systematic review on readmissions highlighted the important role of hospitals in transitional care interventions and the coordination of chronic care to ensure better outcomes for patients and fewer readmissions (85). The review stated that most problems related to continuity of care occurred at transition points involving a lack of cross-boundary continuity between sites or providers, or a lack of flexibility in the coordination when there were major changes in the patients' needs (85). In line with this, our review results underscore the importance of flexible care plans and care coordination between healthcare professionals, especially for people with complex care needs. Additionally, the review contributes with evidence on intervention components that intend to prevent avoidable hospitalizations, and important findings on the challenges related to establishing care continuity and coordination. Further, the findings highlight the importance of addressing motivators and enablers to engage healthcare professionals and people with care needs in preventive interventions.