Search strategy

We searched PubMed, Medline, Science Direct, Google Scholar, Africa Index Medicus (AIM), Africa Journals Online (AJOL) databases to retrieve relevant primary studies conducted in SSA, using pre-defined search (Title/Abstract) and indexing terms (MeSH/Emtree). Keywords and MeSH terms and their combinations used in the searches were “knowledge”, “stroke”, “heart attack”, “coronary heart disease”, “myocardial infarction”, “congenital heart disease”, “heart diseases”, “vascular diseases”. Reference lists of full-text papers were hand searched for additional articles and reviewed for relevance in this review. The strategy is provided as a supplementary file (S1 Text).

Inclusion criteria

We included studies that were published in SSA, in English, and in peer-reviewed journals between 2007 and 2015. Papers were from primary research of any design and methodology: quantitative and qualitative and exploring knowledge, awareness and perception of CVD and the risk factors. Studies that were carried out among SSA populations living in Western countries or only described interventions leading to increased knowledge and awareness of CVDs or risk factors and symptoms of CVDs were also excluded.

Definition of terms/concepts

CVDs include vascular diseases in general, CHD, cerebrovascular disease (e.g. stroke), myocardial infarction (MI) and congenital heart diseases. Individuals were required to correctly identify CVD conditions, risk factors and clinical symptoms from a list to gauge their knowledge. Perception was based on individuals’ self-assessment of chances of developing CVDs, as well as their understanding of who was at risk to develop the condition. Perception was mostly explored in qualitative studies. The SSA region was classified based on the United Nations classification of countries.[19]

Data extraction

Two reviewers (DB, FW) conducted data extraction from the identified studies. Information was extracted on: authors, year of publication, study design and population, research methods, types of CVDs studied, findings on the knowledge, awareness of and perception towards CVDs and the risk factors. We extracted additional data on the factors influencing knowledge and perceptions of CVD and the reported sources of information on CVD and risk factors. The exercise was reviewed by JB and KKG, who were also consulted on the extraction process.

Quality assessment

The quality of the quantitative studies, were assessed based on National Institute of Health (NIH) Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies.[20] This form appraised the reliability, validity and generalizability of the quantitative studies. The NIH quality assessment tool uses 13 criteria to assess and rate the quality of studies. This included the research question, study population, sample size estimation, exposure and outcome assessment, loss to follow-up and statistical analysis. General guidance is provided for determining the overall quality of the studies and to grade their level of quality as good, fair or poor.

Qualitative studies were appraised using the Critical Appraisal Skill Programme (CASP) tool.[21] The CASP tool has 10 items that look at the relevance and clarity of research goals, appropriateness of the research design and methodology in addressing the research question, recruitment strategies, data collection, data analysis, findings, ethical consideration and value of the research. Questions attached to these items enable critical self-reflection about biases and assess the extent to which findings from the study could be transferred to other settings or groups. The quality assessment and criteria are available as a supplementary file (S2 File).

Synthesis of findings

Qualitative data synthesis of the findings on the knowledge, awareness of and perception towards CVD risk and risk factors in SSA was conducted. Findings from the quantitative papers were absorbed using the multi-source synthesis method, an analytical technique that enhances transparency when synthesizing quantitative and/or contextual data, thus providing a platform for comparison between studies.[22] Findings from qualitative articles were integrated with those from the quantitative studies based on similar themes or topics. Due to the heterogeneity in outcomes, data were not pooled to conduct a meta-analysis.

Study characteristics

A total of 2212 titles were identified from electronic database searches. 2167 titles were excluded for being irrelevant to the review question, and 45 full-text articles were assessed for inclusion. Twenty-five articles were excluded based on reasons such as not reporting the link between risk factors to general knowledge and awareness of CVDs or reporting results of an impact of an intervention in the levels of knowledge and awareness of CVD and risk factors. In the end, 20 articles were included in the review. The assessment and inclusion criteria are reported in Fig 1. One of the 18 quantitative studies out of the final 20 studies was quasi experimental, while the rest were cross-sectional. Respondents were recruited from varied settings, including from general population samples living in urban and rural areas, and from specific samples like academic staff, hospital staff and health professionals, patients, and employees in banks and in the military. The age of the participants in the different studies ranged from 16 to 82 years. More information on characteristics of study participants is presented in Table 1.

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Fig 1. Flow chart of inclusion and exclusion of relevant articles.

https://doi.org/10.1371/journal.pone.0189264.g001

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Table 1. Characteristics of included studies.

https://doi.org/10.1371/journal.pone.0189264.t001

Quality of included studies

The majority of the quantitative studies were rated to be of good or high quality (n = 10). They described in detail the design and methodology used, the process of recruiting participants, justification and methods of arriving at required sample size, study setting, clear and detailed presentation of findings. Studies that were rated to be of fair or poor quality (n = 8) were papers that failed to describe details of subject recruitment processes including inclusion criteria and sampling strategies and lacked justification of sample size and other issues that could lead to a high risk of bias and undermine generalizability of the study (S1 File).

Knowledge and awareness regarding cardiovascular diseases

Most studies in this review did not state a priori the criteria used in measuring and classifying levels of knowledge and awareness. However, most of them classified knowledge and awareness of CVD or the risk factors as poor, acceptable or good. In the study by Akintunde et al,[23] among university staff, a knowledge score of <50% was classified as low; 50–69% moderate and ≥70% good. Nakibuuka et al[24], in a study in Uganda classified urban and rural residents who could identify 5–10, 2–4 and <2 CVD risk factors or warning signs as having good, fair and poor knowledge respectively.

Awareness of CVDs was high among studies that reported on it; 76.2% among bankers and teachers[25] and 75.6% among military personnel[26] in Nigeria. Most people in a low-income peri-urban community in South Africa,[27] were familiar with the terminology used to describe CVDs. However, the studies reported generally low knowledge levels of CVDs with most studies reporting less than 50.0% of respondents having good knowledge. In studies conducted among workers in a Nigerian University Hospital, one reported that 19.0% had good knowledge of CVDs[23] while another showed that 53.5% knew the mechanism through which stroke occurs.[28] Findings on the knowledge and awareness of CVDs in SSA is summarized in Table 2 and Fig 2.

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Fig 2. Summary of results.

RF, Risk factors; HT, Hypertension; DM, Diabetes Mellitus; PA, Physical activity; FH, Family History; CVD, Cardiovascular disease; MI, Myocardial infarction.

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Table 2. Outcome assessment and findings of included studies.

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Knowledge of risk factors for cardiovascular diseases

To gauge knowledge of risk factors for CVDs, individuals were required to correctly identify them from a list. Just like it was the case with CVD risk, majority of the studies also reported low levels of knowledge on risk factors for CVDs. Hypertension and stress were the most known and cited risk factors in most of the studies. Participants who were unable to identify a single risk factor for CVDs ranged from as low as 1.8% in a study among hospital staff in Nigeria[29] to a high of 73.0% in a population-based survey in Uganda.[24] Specifically, among studies that looked at stroke, participants who could not identify a single risk factor was <20% among hospital workers,[28,30]university staff[29] and secondary school teachers[31] in Nigeria and 40–80% among rural and urban Ugandans[24,32] and rural Nigerians.[33] A study that looked into coronary heart disease among teachers and bankers in Nigeria also described about 20% of the study population as having no knowledge of risk factors for the disease.[25] The studies also reported some misconceptions regarding the risk factors for CVDs to include evil spirits, demons and will of God as causes of CVDs.[24,28]

Hypertension

Knowledge levels of hypertension as a risk factor for CVD ranged from as low as 16.2% in a study among rural community members in Nigeria[33] to 95.7% in a study among health workers in Nigeria.[28] In a low-income peri-urban community in South Africa, none of the respondents cited hypertension as a risk factor of CVD.[27] Low knowledge levels of hypertension as risk factor for CVDs, ranging from 16.2% to 34.5% were reported among studies conducted within urban and rural communities[32–36] whereas high percentages were reported in studies conducted among health workers (95.7%);[30] (88.6%),[28] secondary school teachers (79.8%)[31] and staff of tertiary institution (91.7%).[29]

Diabetes

The knowledge level of diabetes as a risk factor of CVD ranged from 0.3% in a study among urban adult population in Benin[36] to 47.4% among secondary school teachers in Nigeria.[31] Two community-based studies from Ghana[35] and Uganda[24] reported less than 15% of study participants possessing any knowledge of diabetes as a risk factor for stroke. Knowledge of diabetes as a CVD risk factor among hypertension and diabetes patients at a specialist medical centre in Southern Nigeria was very low, at 7.3%.[37]

Smoking

Knowledge of smoking as a CVD risk factor was 70.6% among military personnel in Nigeria[26] and less than one percent among the general populations in Central Uganda.[24] Less than 50% of respondents across all studies could identify smoking as a risk factor for CVD, with the exception of the study among Armed Forces personnel in Nigeria, 70.6%.[26] In a study in rural Uganda, none of the respondents identified smoking as a risk factor for CVD.[32] In all, 14 studies reported on knowledge of smoking as CVD risk factor, three of which reported <5% with knowledge of smoking as a risk factor for stroke^26,42 and for CHD.[38]

Physical inactivity

Knowledge of physical inactivity or sedentary lifestyle as risk factors for CVD ranged from 0.6%[37] to 57%,[31] in Nigeria. Two other studies reported knowledge level of less than 10%; 1.2% in a rural Nigerian community[33] and 3.8% among hospital outpatients.[37]

Heavy alcohol consumption

Heavy alcohol consumption as a risk factor for CVD was reported by 4.5% in a study among patients with hypertension and/or diabetes at specialist medical outpatient clinics in Nigeria[37] to as high as 52.8% among staff at a University Hospital and same proportion among military personnel in Nigeria.[26] Another study among secondary school teachers[31] and Hospital staff in Nigeria[28] reported 52.6% and 43.4% of knowledge of alcohol as risk factor, respectively. Participants enrolled in qualitative studies conducted in South Africa and Cameroon[27,39] also mentioned heavy alcohol consumption as risk factor for CVD. Respondents in a study among outpatients in Nigeria were, however, not able to identify heavy alcohol use as a risk factor for CVD.[40]

Stress

Stress was reported as a risk factor for CVD by 7.6% of adults in an urban district of Benin[36] to 87.5% of members of Nigerian Armed forces.[26] Other studies conducted among formally employed workers reported high knowledge level; health workers 70.8%,[28] among university staff 80.2%[29] and secondary school teachers 65.8%.[31] Among community level studies, knowledge level of 53.5% as among a South African community[34] whereas studies among urban communities in Ghana[35] and Benin[36] reported low knowledge of stress (22% and 7.6%) respectively.

Other risk factors

Other risk factors for CVD were ageing, family history, obesity and unhealthy diet. Knowledge of these risk factors was low across studies reviewed and was least cited or known among study subjects. Ageing was identified as a risk factor for CVD by 63.8%, 43.9% and 38% among university staff,[29] secondary school teachers[31] and hospital staff[28] respectively in Nigeria. Among the studies that reported on family history, knowledge level was >50% in two of the studies that were conducted among formal working populations in Nigeria,[29,31] 3.2% among medical outpatients in Nigeria[40] and as low as 1.3% in the study conducted among people living with HIV/AIDS in Cameroon.[38] Of nine studies, five that were conducted among people living with HIV,[38] hypertension and/ or diabetes outpatients,[37] rural population,[33] urban population[36] and the general population,[24] <10% identified obesity as a CVD risk factor. The biggest proportion with knowledge of obesity as a CVD risk factor, 56.1% was reported among staff of a University in Nigeria.[29] Knowledge on diet as risk factor for CVD was 99.1% among secondary school teachers[31] and <10% among Armed Forces personnel[26] in Nigeria and the general household population in Uganda.[32] Unhealthy diet was also reported as a risk factor in two studies.[27,39]

Knowledge of symptoms/ clinical signs of cardiovascular disease

The proportion of respondents who could not identify a single symptom of any CVD condition ranged from 7.0% among academic staff in a University in Nigeria[29] to 75.1% among the general population in Uganda.[24] The proportion of respondents who could identify all symptoms ranged from 3.5% among teachers[31] to 15.2% among health staff[29] in Nigeria. Knowledge of chest pain, excessive sweating, nausea, vomiting, and pain, as symptoms of CVDs were also very low (<3%).[38,40] Knowledge of symptoms of stroke was <50% in all the studies that reported on stroke with the exception of three, which reported >50% knowledge level of one (paralysis, 55.6%) among medical outpatients,[40] two (weakness, 52.2%; slurring speech, 61.9%) among hospital staff³¹ and four symptoms (slurring speech, 58.7%; dizziness, 52.8%; numbness, 69.4% and weakness, 69.8%) among university teachers.³² The most reported symptoms of stroke were weakness, 61.9%[28] and 69.8%,[29] slurring speech, 59%[29] and paralysis on one side, 55.6%.[40] Dizziness, loss of vision, chest pain and altered consciousness, headache, vision problem, shortness of breath and numbness were least reported across the studies.

Perception of cardiovascular disease risk

Four studies investigated the perception of CVDs.[24,27,40,41] Among people living with HIV/AIDS, 31% believed they were at high risk of developing CVDs, while older women were more likely to agree that they were at a higher risk for CVDs.[41] In a qualitative study from South Africa,[27] participants were described as being generally unfamiliar with the concept of risk, while the two respondents who were familiar with the concept of risk could also not explain in detail what it actually meant. In a study of medical out-patients in a tertiary health institution in Nigeria,[40] majority (65.8%) of the respondents were never concerned about the possibility of developing stroke, 16.1% sometimes thought of it, 12.3% occasionally and 5.8% always had the concern. 34.1% of respondents in a population-based study from Uganda[24] perceived no chance while 14.4% perceived high chance of possible stroke in lifetime.

Factors influencing knowledge of cardiovascular diseases and risk factors among reported studies

Factors such as age and family history, type of residence and education were reported to be associated with knowledge of CVDs. The significant influence of age on knowledge of CVD was reported by three studies.[29,36,37] In two studies from Nigeria conducted among hospital outpatients[37] and university staff,[29] age <55 and <40 were a significant predictor of knowledge of CVDs. There was a significant relationship between educational attainment and knowledge of CVDs.[17,29,33,36,37,40] As reported in a study from rural South-Western Nigeria,[33] people with tertiary education were three times more likely to be knowledgeable of CVD risk factors and a study among hospital outpatients in Nigeria[37] showed that more than 12 years of education increased the odds of being knowledgeable about CVD risk factors by more than twice. A significant association between type of residence and knowledge of CVD was also described: urban residents were more knowledgeable about CVDs compared to their rural counterparts in a community study in Uganda[24] and a study among diabetic/hypertensive outpatients.[37] No study reported a relationship between gender with knowledge of CVDs.[33,42]

Sources of information on cardiovascular diseases

The sources of information for CVD and risk factors included electronic media like television,[25,26,31,36,41] radio,[26,31,41] and print media in the form of magazines or newspapers,[25,31,41] health care professionals[25,26,31,33,36,40,41] and family members or relatives.[25,31,33,36] The internet was reported as a source of information among secondary school teachers[31] and among people living with HIV/AIDS.[41] Television was the most cited source of CVD information across the studies that reported on it, with a proportion of 31.7% in a study of Nigerian Armed forces[26] to 75.5% in a study among University staff.[29] Healthcare professionals as source of CVD information ranged from 4%[41] to 64.4%[17] in people living with HIV and university staff respectively. In the study among hospital workers in Nigeria,[28] 66.9% and 23.2% of clinical and non-clinical staff had read on CVDs from other sources. Details of the sources of information reported across the studies are presented in Table 3.

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Table 3. Sources of information about CVDs.

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Strengths and limitations

This review presents evidence regarding the knowledge and awareness of CVDs in SSA. To the best of our knowledge, this is the first systematic review of the knowledge and perceptions of CVDs in SSA. Our results are based on a systematic search of five databases, integrating both qualitative and quantitative evidence on the topic. The inclusion of qualitative studies in this review meant that research findings on perceptions towards CVDs were incorporated and contributed to our understanding of and explanation of the trends of knowledge of CVDs in this study setting. As the criteria of measurement of knowledge of CVD (risk factors) was not uniform across studies (different criteria were used for classifying knowledge into low, medium or high resulting in heterogeneity across study findings), a meta- analysis could not be conducted. As the study populations differ considerably within and between countries it is difficult to disentangle to what extent educational level or cultural or country level determine knowledge and awareness levels. Still, the qualitative synthesis of available evidence of knowledge and perceptions of and perception towards CVD risk and risk factors presented in this review should speak to the current situation as most studies were published.