Background and aim

The World Health Organization (WHO) defines aHT as a persistent systolic blood pressure (SBP) ≥ 140 mmHg or diastolic BP (DBP) ≥ 90 mmHg. An estimated 1.28 billion adults aged 30–79 years worldwide have aHT, two-thirds of them living in low- and middle-income countries. Modifiable risk factors include unhealthy diets (excessive salt consumption, saturated fat and trans fats, low intake of fruits and vegetables), physical inactivity, consumption of tobacco and alcohol, and overweight or obesity. Non-modifiable risk factors include a family history of aHT, age over 65 years, and co-existing diseases such as diabetes or kidney disease. aHT is the largest modifiable cardiovascular risk factor (CVRF) globally and the leading cause of the 22.9 million deaths attributed to cardiovascular diseases (CVDs) each year in sub-Saharan Africa [1,2,3].

Prevalence of aHT is highest in the African region, where an estimated 27% of the population aged 30–79 years have aHT [4]. However, despite an increasing burden of CVDs, aHT awareness, diagnosis, treatment and control remain low [5,6,7,8]. Barriers to aHT control exist at patient and health system levels [9, 10]. Major challenges for people living with aHT relate to the asymptomatic nature of the condition, leading to a delayed diagnosis and treatment initiation. Once diagnosed, aHT requires lifelong lifestyle modifications, frequent medical check-ups, ongoing counselling and regular adaptation of treatment dosage or drug regimen [9, 11]. Regional health systems remain poorly adapted to provide comprehensive CVD care, with insufficiently trained, equipped and supported workforce, limited availability of treatment options, and infrequent or non-existing monitoring of treatment outcomes, such as BP control and end-organ function [8, 12].

As aHT is a prevalent, chronic and, often, asymptomatic health condition, successful care models must be easy to access and provide long-term medical follow-up [13,14,15,16]. Community-based health services have been proposed as solutions to bridge existing barriers in access and to scale up services for aHT [17,18,19]. These care models frequently promote task-shifting/sharing, simplification of clinical care algorithms and integration of other services [20,21,22,23,24,25]. Although the terms task shifting and task sharing are sometimes used interchangeably, task shifting is defined as a systematic and planned transfer of care duties from physicians to non-physicians, such as nurses, or community health workers [26], whereas task sharing describes professionals working together to deliver health services. In practice, this implies that when physicians are not available, care tasks must be shifted to non-physician workers for the health system to function. When a few physicians are available, tasks may be shared with other health-care professionals with some supervision or referral to physicians [27, 28].

To date, community-based and out-of-facility care models have been applied to scale up treatment for HIV and tuberculosis (TB), with different success [29,30,31,32,33,34,35]. However, currently, there is no consensus nor guidance on how such models should be structured to have substantial impact in aHT care. Similarly, evidence to understand how, and to what extent tasks could be shifted to lower cadre health care providers, and how services could be decentralized is lacking. A preliminary search of MEDLINE, the Cochrane Database of Systematic Reviews and the Joanna Briggs Institute (JBI) Evidence Synthesis revealed no systematic reviews or similar scoping reviews on this topic. To inform future research, public health programs, and policies, this literature scoping review aims to catalogue the existing community-based aHT care models for non-pregnant adults in sub-Sahara Africa.

Methods

We chose a scoping review methodology to provide an overview and a categorization of existing knowledge, rather than a narrow synthesis of a predefined research question. Typically, scoping reviews are used to map the key concepts that underpin a field of research, as well as to clarify working definitions, and/or the conceptual boundaries of a topic. In this scoping review, the authors explore the breadth of the literature, map and summarize the evidence, and inform future research in the topic [36]. We followed the framework proposed by Arksey and O’Malley [37], further developed by Levac et al. [38] and the Joanna Briggs Institute [39]. The protocol has been published [40]. Our primary objective is to construct a framework to categorize these aHT care models. Secondary objectives include: 1) to appraise the models of care, in terms of acceptability, BP control, engagement in care, and occurrence of end-organ damage, 2) to describe within-study comparisons between community-based and facility-based models of care, if provided by authors and 3) to identify gaps in the literature with respect to community-based service models for aHT.

We included studies in which participants were non-pregnant adults ≥ 18 years, diagnosed with aHT and living in sub-Saharan Africa. A summary of eligibility criteria is available in Table 1. Included studies had to report medical management and treatment for aHT that differed from conventional facility-based care in terms of provider cadre, location, or frequency of follow-up visits. Interventions had to address general management and medical treatment for aHT, including lifestyle modification, self-care, treatment administration and screening or management of organ complications. Included studies had also to report on at least one of the following outcomes: acceptability of the care model, BP control, engagement in care, or end-organ damage. We did not include studies where only aHT screening or diagnosis was reported. Studies where the intervention was a mere add-on and did not replace, at least partly, facility-based care, or did not reduce the frequency of visits to a professional health care worker, were not eligible. We also excluded studies that reported the pilot experience of a published intervention, if the model of care was the same.

Table 1 Study inclusion and exclusion criteria
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A first literature search was conducted on 23 May 2021. The search was repeated on 15 October 2021, yielding no further eligible studies. The literature search strategy was drafted and refined through discussions with the study team and an experienced scientific information specialist (JH), then reviewed by a second information specialist (CA). The search strategy was first developed in Embase Elsevier [41], and subsequently translated for the databases Medline Ovid [42], Cumulative Index to Nursing and Allied Health Literature (CINAHL) [43], and Scopus [44]. Detailed information on the search strategy and is available in Annex 1.

No language limits or date restrictions were applied. Conference abstracts where no peer-reviewed publication was available were excluded. The search results from each database were imported to EndNote X9 and deduplicated according to the method of Bramer [45]. Two independent reviewers (LG, ER) individually assessed study titles, abstracts, and full texts against the predefined eligibility criteria of the review. Authors were contacted when the description of the model of care was unclear or incomplete to decide on inclusion or exclusion. Backward and forward citation from included studies was used to identify additional articles that met the inclusion criteria. Disagreements were resolved through discussions between the two first authors (LGF, EF) and the last author (NDL).

Data extraction was independently conducted by two authors (LG, ER) using a tool created in Word™v.16.0 and piloted on three studies. Information included author, year of publication, study design, target population, location of study, duration of follow-up, type of community-care model, health provider cadre, outcomes measured and comparison arm if available. All reported variables were described as the authors defined them, with no other assumptions. Discrepancies between reviewers were discussed and solved by consensus. The information was chartered in Excel™ v16.0.

We summarized each study’s outcomes and, where possible, we pooled outcomes and reported average, range and/or median values. If models of care were similar, we grouped results by intervention type and reported common features, such as health cadre providing the service, location of delivery and frequency, use of e-Health, or integration with other chronic conditions. Assessment of quality of the included evidence was not initially planned, and thus not specified in the published protocol. However, we undertook the analysis at a later stage to comment on recommendations for evidence generation in the field. We assessed the quality of the included cohort and case–control studies using the Newcastle–Ottawa Scale [46]. The domains of the tool rate the selection of participants, comparability, and outcomes, to a maximum of 9 points. Whereas this scale is widely used to assess the quality of observational studies, there are no established thresholds to define “poor” or “good" quality of a study. Based on a recent literature review, we applied a threshold ≥ 6 as “no high risk of bias” [47]. Randomized controlled trials (RCTs) were judged using the Cochrane Collaboration’s tool to assess RCTs [48] and cluster RCTs [49]. We evaluated the sequence generation, participant recruitment with respect to randomization timing, deviation from intended intervention, completeness of outcome data for the main outcome, bias in the measurement of outcome, and bias in the selection of the reported result. Additionally, we addressed both quantitative and qualitative gaps in the literature and proposed suggestions for further studies and applications for programmatic scale up. The results of the review are documented in accordance with the PRISMA-P reporting checklist [50].

Using the reported experiences, we conceptualized a framework containing six building blocks to design and describe community care models for aHT.

Results

Search results

Literature search and deduplication yielded a total of 4,618 citations (Prisma Fig. 1). Titles and abstracts screening resulted in a first classification, after which 76 papers were included for full-text review. Reasons for exclusion at full-text screening included: studies described models with most of the aHT care happening at facility level (n = 6); the description of the model of care lacked details on the content of the intervention (n = 4); studies piloted a model of care that was further described in an included study (n = 4); and the described model of care or outcomes did not match the inclusion criteria (n = 53). Backward and forward citation searching of included studies yielded 333 additional references; all of them were screened, and three new studies were identified. As a result, 12 references were finally included [51,52,53,54,55,56,57,58,59,60,61,62].

Fig. 1
figure 1

Studies selection PRISMA diagram. From: Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ 2021;372:n71. https://doi.org/10.1136/bmj.n71. https://doi.org/10.1136/bmj.n71, For more information, visit: http://www.prisma-statement.org/

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Characteristics of the studies

Characteristics of included studies are available in Table 2. Identified studies were published between 1994 and 2021, and seven (58%) were published after 2017 [52,53,54,55,56,57, 59, 61] (Fig. 2). Eleven (92%) were single country studies [51,52,53,54,55,56, 58,59,60,61,62] whereas one [57] implemented the same service model in two countries. West African populations were represented in four (33%) [52, 55, 59, 60], East African populations in five (42%) [53, 54, 56, 58, 61], Southern African populations in two (17%) [51, 62] studies and one (8%) study presented results from both East and West Africa [57] (Fig. 3). Seven (58%) studies were conducted in urban areas [51, 54, 55, 58,59,60,61], three (25%) in rural areas [53, 56, 62], one (8%) study [52] took place in semi-urban areas and one (8%) [57] study reported findings in urban and rural settings. No studies reported interventions in special settings, such as remote, hard-to-reach populations or conflict areas.

Table 2 Baseline characteristics of studies
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Fig. 2
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Included studies by year of publication

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Fig. 3
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Included studies by country

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The majority were before-after studies, describing post-intervention outcomes [52,53,54, 57, 58, 60, 62] (7, 58%). Other designs included: case-control [51] (1, 8%), mixed-methods [61] (1, 8%), prospective non-randomized controlled trial [55] (1, 8%), RCT [59] (1, 8%), and cluster RCT [56] (1, 8%). The primary aim of most of the studies was to test a specific intervention adapted to a particular context [51, 55,56,57, 59,60,61,62] (8, 67%), while, four (33%) studies were part of broader health or non-communicable chronic disease (NCD) implementation projects [52,53,54, 58]. Sample size varied from 42 to 7188 participants, with five (42%) studies including more than 1000 participants [52, 56,57,58, 62]. The majority of the studies (10, 83%), narrowed the inclusion criteria to participants with uncomplicated aHT [52,53,54,55,56, 58,59,60,61,62]. A total of seven (58%) studies had no comparator arm [52,53,54, 57, 58, 60, 61], whereas five (42%) provided intra-study comparisons of interventions [51, 55, 56, 59, 62], with either standard of care [51, 55, 59] or a second intervention [56, 62].

Models of care

Four different service delivery models were described: services provided by community pharmacists [52, 55, 60, 61], temporary or permanent stations placed at strategic and accessible locations in the community [54, 62], routine facility-based care complemented with home visits or services in other community locations to reduce patient visits to the facility [51, 57, 59], and care provided at the time of collecting medication in aHT treatment groups [53, 56, 58]. All models applied different elements of task shifting or task sharing. Medical specialists, including cardiologists or general doctors, had a substantial role in supporting the services in seven (58%) studies, either managing referred patients or supporting the practice of lower cadres [51, 52, 54, 56, 57, 61, 62]. Among non-physician delivered services, aHT care was delivered by nurses [51, 52, 54, 56,57,58,59, 62] (8, 67%), community health workers [51,52,53,54, 56, 57] (CHW) (6, 50%) or pharmacists [51, 52, 55, 56, 60, 61] (5, 42%). For each model of care, authors described the preparation and training given to the health workers involved. Most commonly, an initial training session included training on BP measurement technique, healthy lifestyle, clinical guidelines, counselling and support techniques, and familiarization with the information capturing tools. Sessions were longer for lay cadres and shorter for health professionals and only three (25%) provided ongoing mentoring or supervision [57, 59, 60].

Five (42%) studies specifically reported on aHT medical treatment regimens [52, 56, 57, 60, 62] (Table 3). Treatment choices reflected historical and context recommendations, as well as, availability of drugs. Most frequently, treatment algorithms used diuretics, calcium channel blockers (CCB), ß-blockers, angiotensin-converting enzyme (ACE) inhibitors, and angiotensin receptor blockers (ARBs). Treatments included the use of monotherapy and combinations, however, none used fixed dose combinations.

Table 3 aHT drug regimens used in the included care models
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Seven (58%) studies integrated aHT care with other prevalent chronic health conditions, mostly diabetes [51, 53, 55, 56, 58], and HIV [58]. Only two (16%) models integrated care with other NCDs, such as mental health, epilepsy, asthma, or heart disease [53, 59]. Five (42%) studies used electronic information systems as a substantial component of the model of care, including clinical and computerized decision support systems or e-health platforms [52, 55, 57, 60, 61].

Measured outcomes

Table 4 summarizes the studies’ outcomes of interest, perceived benefits, and challenges of the models of care, as described by the authors. Two (17%) studies reported on acceptability of the care model [60, 61]; eleven (92%) on BP control [51,52,53, 55,56,57,58,59,60,61,62]; and 10 (83%) on engagement in care [52,53,54,55,56, 58,59,60,61,62]. Only one (8%) study reported on end-organ damage. Nine (75%) studies report outcomes between an average follow up of 6–12 months [51, 52, 55,56,57,58,59,60,61], while 3 (25%) studies reported a follow up longer than one year [53, 54, 57].

Table 4 Studies reported outcomes and key findings
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Acceptability was reported either collecting the experience of the health workers [61], or measuring patients’ satisfaction through qualitative research and the Larson satisfaction questionnaire [63]. Of the two studies reporting satisfaction, one model delivered home-based aHT treatment and one provided care in community pharmacies [60, 61]. Participants reported benefits in adhering to the treatment and general knowledge on self-care practices.

With regards to reporting BP control, targets for (SBP, (DBP and aHT definitions varied, reflecting historical definitions [62] or pragmatic targets linked to inclusion criteria in the care model [53, 58]. Seven (58%) studies [52, 55,56,57, 59,60,61] used SBP ≤ 140 mmHg and DBP ≤ 90 mmHg to define BP control, while two (16%) [55, 61] modified control thresholds for diabetic patients. Eight (67%) studies showed a significant improvement in BP control [51, 52, 55, 57, 58, 60,61,62] and one (8%) showed that BP was controlled in higher proportion for diabetic patients receiving community-based services [51].

Eight (67%) studies reported engagement in care [51, 52, 54,55,56, 58, 59, 61] using different measures: lost to follow-up or death [54, 58], self-reported adherence to the treatment [54, 55, 59,60,61], regular use of the e-health support platform [61] or attendance to follow up visits [51, 52, 56, 58]. Two (16%) community pharmacy models in West Africa were the only ones that reported significant improvements in engagement in care and adherence to aHT treatment [55, 59], whereas two studies suggest that community care posts and home-based care could increase long-term engagement in aHT care [52, 54].

The only study reporting end-organ damage measured serum creatinine as surrogate marker for renal function. In this care model, laboratory tests were offered at the time of patients group meetings and collection of aHT medication in a subset of participants [58].

Authors reported the perceived benefits of the aHT models of care in relation to the health system and the users. Benefits for the health system included: task-sharing across different professionals, decrease in daily patients load at facilities, and possibility to offer wider access for services and prevention of other CVDs [51, 53,54,55,56,57,58,59,60,61,62]. Perceived advantages from the patients’ perspective referred to increased flexibility to access services, and reduction of costs and waiting times [51, 53,54,55, 57, 58, 61]. One study noted positive impacts in patients’ quality of life, as the model of care addressed broader social determinants of health closely linked to CVDs, such as poverty, rather than just providing aHT treatment [56].

Authors also reported the weaknesses of these aHT care models. Doubts on generalizability of the models arose in relation to strict inclusion criteria, as care was provided either to selected groups or clinically stable participants. Seven (7, 58%) used clinically narrow eligibility criteria, excluding patients with complicated aHT, severe conditions, or comorbidities [53, 54, 56,57,58, 61]. One study in South Africa provided care only to the privileged white population during Apartheid [62]. High attrition rates through lost to follow-up and mortality, deficiencies in data quality, small sample sizes, short follow-up periods, or lack of control arms compromised the report of accurate outcomes and the capacity to provide a more complete picture of the real benefit of these models [52,53,54,55, 57, 59, 60, 62]. Poor sustainability of care models was brought up in relation to the use of vertical, non-integrated interventions, including parallel remuneration of health workers, lack of staff, medication stock outs or difficulties in managing and sustaining eHealth solutions [51,52,53, 55, 60, 61]. The overall quality of provided services was a common concern to authors, including difficulties in providing ongoing supervision and mentoring of lower cadres [51,52,53,54,55]. Specifically, the models testing services at community pharmacies in West Africa expressed concerns about the capacity to contribute to a substantial change in service delivery, as the strategy was too far away from existing policies and standards, and sustainability was heavily associated with motivation and remuneration of professionals [55, 60].

Quality of evidence

Nine cohort studies and one case control study were evaluated using the Newcastle–Ottawa scale [64,65,66] (Table 5). All studies scored below 6, mainly driven by very narrowly selected study populations and the absence of comparators in many of the studies. One RCT and one cluster-RCT were assessed using the Cochrane Collaboration’s tool for assessing risk of bias in RCTs [48, 49] (Table 6). Overall bias assessment was “low risk for bias” for one study and “some concerns” for the other.

Table 5 Risk of bias assessment for cohort and case–control studies (Newcastle–Ottawa Scale)
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Table 6 Risk of bias assessment for single arm and cluster randomized trials (Cochrane Collaboration’s tool)
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Discussion

To our knowledge, this scoping review is the first comprehensive analysis of community-based aHT treatment models in sub-Saharan Africa. We systematically compiled and synthesized the current evidence related to service delivery models for aHT treatment that differ from traditional, facility-based care between 1993 and 2021. The increasing number of publications in recent years indicates that this is an active field where rapid developments can be expected in future [67,68,69,70,71]. We identified 12 studies that described one or more outcomes of interest from four distinct types of community-based aHT service delivery in five countries. However, only a minority of studies (4, 33%) compared alternative models to conventional care or to other interventions, making it difficult to draw solid conclusions about the overall effectiveness of these models on clinical outcomes. Due to the wide heterogeneity of the models of care, inclusion criteria, outcome definitions, participants follow up and study types we only described each of the studies individually, rather than providing aggregated statistics.

In the process of summarizing the literature for this scoping review, we abstracted the main elements that integrate the models of care, as described by the authors (manuscript tables). These elements constitute the “building blocks” of each care model and are represented in Fig. 4: cadre of health care provider (who delivers the service, including self-care), target population (for whom the care model is created), location of service delivery (where is the service provided), components of the service package, information systems (methods used for collecting information about the users and the service), and the timing of service delivery (when is the service available to the user). Each of these elements is intrinsically composed by other components. i.e.: in the “information systems” category, different models use either paper-based/digitalized patients’ files/cards and/or digital technology. We propose the use of these building blocks to either design or analyze care models for aHT and in general CVDs. To tailor a model of care to a given setting, each of the six blocks should be taken into account and adapted, considering different aspects, such as: setting, resources, cultural preferences, or specific needs of the target population (Fig. 4). Similar models have been used to scale up tuberculosis or HIV services [29, 72,73,74,75,76].

Fig. 4
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A framework for design of aHT service models, considering their building blocks or main integrating elements

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The West African experiences mostly integrated pharmacists and microfinance solutions in urban areas, while East and Southern African models tested interventions that increased access to care in rural communities. In all service models, care is most often provided by lower cadres of health workers, decreasing frequency of interactions with routine services, and combining a high level of self-care. However, most of the models only included participants with already an acceptable BP control, had a short follow-up period, and failed to provide comparable performance with facility-based care in the same setting. Although it is hard to evaluate their real impact, the reported care models do not seem to be associated with lower user’s satisfaction or worse treatment outcomes.

Beyond clinical indicators that report individual aHT treatment outcomes for participants receiving care in these models, a few studies collected patients’ and service providers’ perspectives. Future studies should seek a combination of quantitative and qualitative data and possibly socio-economic data to understand the real reach and impact of such models. The use of electronic information systems becomes an important part of the care in the most recent studies. Patients receive reminders for adherence to medication, general lifestyle counseling or provision of personalized risk-based care plans through, phone calls, SMS, or use of other e-Health platforms. Similarly, these systems support communication between medical specialists, nurses and lay workers [52, 53, 55, 56, 60, 61].

One interesting finding of this review reinforces the idea that expanding the provision of chronic aHT care, and probably other chronic health conditions, to health workers and structures that are outside of traditional care in facilities, reduces, but does not eliminate the need of care provided by medical doctors or specialized nurses. Rather, these services can be used to provide referral paths to manage patients that need to be evaluated for more complex comorbidities or new cardiovascular events by specialised health workers. Our findings describe diverse and heterogenous models of care and suggest that each setting requires its own specifically adapted model of care, taking into account the six building blocks after careful analysis of local gaps and needs. As such, there is not just “one size fits all” care model to efficiently expand out-of-clinic aHT management.

In an effort to close the global aHT treatment gap and improve BP control at societal level, in 2021 the WHO issued updated guidelines for the pharmacological treatment of aHT in non-pregnant adults [3]. These new global recommendations guide decisions such as the threshold for the initiation of pharmacological aHT treatment, choice of treatment regimens and drug combinations, frequency of patients follow up, BP control targets, and the cadre of providers who may initiate or manage long-term treatment. However, regarding frequency of patients’ follow up and treatment by nonphysician professionals these recommendations remain conditional due to low-certainty evidence. Through scoping the published literature on this topic, we have identified additional research questions where future research could help establishing evidence-based recommendations to scale up similar aHT models of care. First, the development of standard descriptions of the models of care, taking into account the six building blocks, definitions of inclusion criteria of participants and clinical outcomes will be needed. Second, as aHT is a chronic condition, it will be important to understand the use of these models to achieve and maintain BP control beyond the first 12 or 24 months of enrolment, and even longer follow up. Third, to understand the potential of these models to improve BP control at population level, it will be important to describe the patterns of transition between conventional aHT care and one or subsequent alternative models across years of care. Fourth, investigators could provide a description of the capacity that each model of care has to reach BP targets after a period of uncontrolled BP and to integrate care for important co-morbidities, like diabetes, HIV, or tuberculosis. Fifth, reports should aim to demonstrate a decrease of overall risk in CVD events and aHT-related end-organ damage. Sixth, studies should also include a description of the wider hypertensive population, not included in these models, including their treatment outcomes for reference comparison. Lastly, the reporting of costs and cost-effectiveness will be crucial to mobilize investments that can catalyse a significant scale up of these services.

Strengths and limitations

Our review provides a comprehensive description and evaluation of the published community-based aHT care models, following a structured methodological framework. Equally, this review has several limitations. The concept of non-traditional, outside-of-facility health service is heterogenous, poorly defined and lacks standard terminology. Our search terms included most common related synonyms, however, despite the efforts to develop a broad literature search strategy following PRISMA guidance, the selection of standard search terms and databases may have excluded some relevant publications. Our search also excluded regional databases and grey literature; therefore, it is possible that we have missed evidence provided by interventions used in practice and not published. Lastly, we could have missed relevant data when the authors failed to provide sufficient details or disaggregated results [69, 77,78,79,80].

Conclusions

The search for efficient and sustainable service delivery models for the management of aHT in sub-Saharan settings, outside of conventional care, is a rapid evolving field. This scoping review has identified different community-based models that can potentially be seeds of scalable programs that integrate comprehensive chronic care.

However, the wide heterogeneity of the studies, lack of standardization of definitions and measurement of outcomes, small number of participants, short follow up, and lack of reliable comparisons with standard of care, does not allow to describe their real impact in achieving long-term BP control and overall CVD risk decrease. The available literature does not provide a sound basis for policymakers and implementers on whether, and in what form, community-based care delivery models for aHT could be applied to counteract the growing CVD burden in sub-Saharan Africa. We propose that future projects and studies implementing and assessing community-based models of aHT care are designed and described according to six building blocks defining the providers, target groups, components, location, time of services and their use of information systems.