CARDIOVASCULAR JOURNAL OF AFRICA • Volume 34, No 3, July/August 2023 AFRICA 145 study also demonstrated an exponential quadrilinear increase in admission and death rates, reflecting the increasing burden of CVD and its risk factors in the general population. We found a CVD death rate of 30.4% with a case-fatality rate of 24.6%. Similar studies in Nigeria have reported CVD death rates ranging from 16 to 34%. This wide variation could be methodological as most of the studies reporting higher death rates had older subjects, with a mean age above 65 years. Our death rate aligns with the global data that CVD deaths account for about one-third of global deaths.1 Our study also demonstrated that the CVD case-fatality ratio was higher in males. The median age of our study population was 56.6 (46.0–68.0) years, comparable to findings from other studies.22-24 The median age of less than 60 years from our study population further buttresses the point that CVD events occur earlier in LMICs compared to HICs, where they occur more in individuals above the age of 60 years.9,10 This has been attributed to a mix of a huge burden of poorly controlled CVD risk factors, health inequalities and weak health systems.26 The gender distribution of CVD-related admissions from our study was similar, although for heart failure admissions, females were predominant and were also relatively younger. Similar studies have documented female preponderance in their cohorts.27-29 The contribution of peripartum cardiomyopathy, an all-female disease, in the aetiology of heart failure, might be responsible for this female predominance. Stroke was the commonest cause of admission, constituting 51.2% of all CVD admissions, followed by heart failure and HDx. Reported stroke admission rates as a sub-set of CVD admissions in the published literature ranged from 24.3 to 54.6%.22,24,29,30 A few other studies have reported heart failure as the commonest cause of admission.23,29,30 Heart failure admissions in our study constituted 36.2% of all CVD admissions. In Nigeria, heart failure admission rates ranged from 17.4 to 43.3%.22-24,31,32 In Ghana heart failure admissions are quite rife, accounting for about 80% of all CVD admissions.25,33,34 In these Ghanaian studies strokes were not included as outcomes of interest. If stroke is excised from our data, the heart failure admission rate would be 73.7%, comparable to rates from Ghana. Over the decades, the prevalence of heart failure in Africa has risen from less than 10% to the high values reported in some of the studies cited above.35 This increase is not unconnected with the rising prevalence of both behavioural (smoking, unhealthy diets, physical inactivity and psychosocial stress) and biological (hypertension, dyslipidaemia, obesity and diabetes) risk factors for CVD, occasioned by the consequences of epidemiological transition and westernisation of lifestyles.4 In addition, these risk factors are poorly controlled due to health inequalities and fragile health systems.26 The high burden of stroke from our study aligns with the established fact that SSA has the highest burden of stroke globally.36 In the Stroke Investigative Research and Educational Network (SIREN) study,37 hypertension had the highest population-attributable risk of 90.8% (95% CI: 87.9–93.7) for stroke in SSA, higher than what was reported in the INTERSTROKE study.38 In Nigeria, hypertension accounts for about 80% of all cases of stroke.39,40 Our earlier study on ER deaths also reiterated the burden of stroke and its mortality burden in hypertensive patients.20 In the general population, the burden of hypertension in Nigeria is mirrored by its high prevalence, low awareness, low level of optimal control and high level of poor adherence to medications for control.41-44 These interrelated factors invariably drive stroke/ CVD risk and burden. In addition, hypertension frequently co-occurs with other CVD risk factors such as dyslipidaemia, abnormal blood glucose profile/diabetes and obesity.45,46 The relative individual contributions of these risk factors and in synergy increase stroke risk and other CVD sub-types. They also hinder effective control of hypertension.47,48 Similarly, hypertension is the commonest cause of heart failure in Africa. In the Sub-Saharan Africa Survey of HeartFailure (THESUS-HF) study, a nine-African nation study, and the International Congestive Heart Failure study (INTERCHF), hypertension was responsible for 45.5 and 35% of all heart failure admissions, respectively.49,50 However, in the Democratic Republic of Congo and Rwanda, DCM rather than hypertension was the most prevalent heart failure aetiology.51,52 A recent meta-analysis on the aetiology of heart failure in SSA reported that 39.2% of cases of heart failure in Africa were caused by hypertension.53 Nigeria shares a similar fate. Hypertension accounts for between 56.3 and 78.5% of cases of heart failure.22,24,54 In our study it accounted for 49.1% of all heart failure admissions. DCM was another frequent cause of heart failure after hypertension, accounting for 37.0% of all heart failure admissions. In other parts of SSA, DCM is the most prevalent aetiology of heart failure admissions, accounting for 24.1 to 48% of heart failure admissions.51-53 However, our figure is higher than the 18.8% reported by the THESUS-HF study and the 12.0% reported by the INTER-CHF study that included Africans.49,50 The higher prevalence of DCM from our study might be methodological. Our cohort might have included previously unknown hypertensives presenting in heart failure with normal or low blood pressure but with a DCM phenotype on echocardiography. This is possible because hypertension can lead to DCM.55 PPCM, a type of DCM, accounted for 4.1% of all cases of heart failure and 10% of all DCM causes of heart failure, respectively, in our study, comparable with the 7.7% from the THESUS-HF study and the 5.3% from the Abuja Heart Failure study.23,49 With regard to mortality, we found a CVD mortality rate of 30.4% over the period under review. CVD mortality rates in published local data range from 10.3 to 33%.22,24,29,30,56 In SSA, the CVD death rate was 38.3% in 2013 and stroke was the greatest contributor.56 A recent 10-year review of CVD admissions (predominantly heart failure) in Ghana reported a death rate of 23.1%.22 In our study, stroke was the greatest contributor to mortality with a mortality rate of 35.7%. In Nigeria, death rates from stroke in CVD admission studies ranged from 10.3% to 33%.22,24,30,31,57 Higher mortality rates have been reported in standalone stroke registries.39,58 Across SSA, stroke admissions and mortality rates have been on the increase in the past three decades, largely due to an ageing population experiencing epidemiological transition and its attendant plethora of CVD risk factors, especially hypertension.58-61 Stroke also had the shortest length of hospital of stay 10 days and the highest seven-day mortality rate of 66.7% in our study. This high rate of early mortality may be due to late presentation of stroke cases at the hospital and the absence of a dedicated acute stroke unit at the time of this study. Stroke is the
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