Insufficient control of blood pressure in the population of Nigeria and Africa

Burden of insufficient blood pressure control

It is a fact that the prevalence of hypertension is high and the overall awareness of raised BP among hypertensives is low both in Nigeria and in Africa as a whole. A report from one of the largest synchronised standardised multinational screening campaigns on hypertension, May Measurement Month (MMM) 2017, where 1.2 million people were screened, showed that mean systolic and diastolic pressures and the proportion of participants with hypertension were highest in sub-Saharan Africa (SSA). A reported 35,585 (28.3%) participants from SSA had hypertension, 23,476 (20.6%) participants from SSA were hypertensive and not receiving treatment, while 6,601 (55.9%) hypertensives receiving treatment were not controlled [4].

Notably, Nigeria is the worst hit in terms of having a higher prevalence and lower treatment figures compared to overall rates for Africa, though control rates are similar. In the same study, data for Nigeria showed that 36.2% of adult Nigerians were hypertensive, 12.9% of all the participants were on treatment and almost 60% of those receiving antihypertensive treatment had uncontrolled BP [5]. The findings from this study are comparable to recent randomised surveys and opportunistic screenings in various parts of the country. A systematic review and meta-analysis of population-based studies from January 1980 to December 2013 which provided estimates on the prevalence of hypertension in Nigeria by Adeloye et al estimated an overall hypertension prevalence of 28.9% (25.1, 32.8) while the pooled awareness rate of hypertension was 17.4% (11.4, 23.3) [6]. 

The morbidity and mortality associated with hypertension cannot be overemphasised in SSA where, in a recent study, Forouzanfar et al reported that the prevalence of hypertension increased substantially between 1990 and 2005 with a corresponding increase in disability-adjusted life years (DALYS) and deaths related to hypertension for all causes, as shown in Table 1. The largest number of systolic blood pressure-related deaths per year was due to ischaemic heart disease, haemorrhagic stroke, and ischaemic stroke [7].

Table 1. Projected number of disability-adjusted life years (DALYs) and deaths related to systolic blood pressure of 140 mmHg or higher for regions of Africa and Nigeria. 

Projected number of disability-adjusted life years (DALYs) and deaths related to systolic blood pressure of 140 mmHg or higher for regions of Africa and Nigeria. Data are for individuals aged 25 years and older, both sexes combined, and for the years 1990 and 2015.

Adapted with permission from Forouzanfar MH, et al. Global burden of hypertension and systolic blood pressure of at least 110 to 115 mmHg, 1990-2015. Published with permission from JAMA. 2017;317:165-182. doi:10.1001/jama.2016.19043 [7].

Causes of insufficient blood pressure control

Numerous reasons have been considered responsible for why we fail to achieve and sustain sufficient BP control among known hypertensives in our practice. However, important among them are the following.

Poor drug adherence

The finding of an elevated BP should always lead clinicians to search for the cause(s), particularly the most common ones such as non-adherence or poor adherence to the prescribed treatment regimen. In Nigeria and in Africa as a whole, many known hypertensives engage in this unhealthy habit as a result of insufficient patient education about dosage, duration and the side effect profile of antihypertensive medications. Because of the asymptomatic nature of hypertension, long-term medication adherence is poor. Some patients self-medicate or take drugs only when symptomatic. Other reasons given are the relatively high cost of medications, as well as lack of motivation and social support etc.

White-coat or masked hypertension phenomenon

White-coat hypertension is a condition in which office BP is elevated but patients have controlled ambulatory BP measurement (ABPM) or home BP measurement (HBPM), while masked hypertension is when office BP is normal but ABPM or HBPM is elevated according to guidelines. These are conditions which often confuse patients in our setting, and they are therefore reluctant to take their medications if they fall into these two categories. In these instances, detailed health education and counselling have to be given to such patients, enlightening them about proven morbidity and mortality associated with the two conditions as well as the beneficial effects of their BP-lowering medications [8].

Clinical inertia

It is recommended that the first objective of treatment should be to lower BP to <140/90 mmHg in all patients and, provided that the treatment is well tolerated, treated BP values should be targeted to 130/80 mmHg or lower in most patients [3]. However, some clinicians in Nigeria and Africa as a whole are reluctant to use multiple antihypertensives to lower the BP to recommended values, especially in cases of resistant hypertension. Lack of local treatment guidelines can contribute to clinical inertia.

Clinical factors

In the clinical setting, poor office BP measurement technique, including the use of cuffs that are too small relative to the arm circumference as well as marked brachial artery calcification, especially in older and/or diabetic patients, can result in a spurious elevation of BP. Lifestyle factors, such as obesity or being overweight, obstructive sleep apnoea (usually, but not invariably, associated with obesity), undetected secondary forms of hypertension and hypertensive patients with already advanced hypertension-mediated organ damage (HMOD), particularly chronic kidney disease (CKD) or large-artery stiffening, are other conditions known to contribute to insufficient BP control.

Comorbidities

There is substantial interplay of metabolic factors with hypertension. Optimal control of blood pressure may be blunted by coexisting metabolic risk factors such as hyperglycaemia, dyslipidaemia, hyperuricaemia, etc., clustering the phenotype of metabolic syndrome. Thus, the phenotype of metabolic syndrome is associated with a high likelihood of uncontrolled BP, despite a greater number of prescribed medications; therefore, other metabolic conditions need to be treated to achieve normal BP control.

Low awareness rate

The low hypertension awareness rate of 17.4% in Nigeria [6] reflects the general African situation and contributes significantly to the high hypertension burden in SSA [4]. This situation is compounded further by the widespread lack of management guidelines and hypertension registries at health facilities, as reported in a national survey of health facilities in Uganda [9]. As a result, the ability to monitor awareness, prevalence, treatment and control rates is greatly limited.

Poverty and out-of-pocket payment mode

Effective antihypertensive medications are out of the reach of most Nigerians. This is because nearly half of its estimated 180 million population now live in extreme poverty (below $1.90 a day) [10]. The fact remains that the majority of citizens pay for health services through out-of-pocket means except for roughly 4.5 million people, representing 3% of Nigeria’s population, who are under the National Health Insurance Scheme (NHIS), and most of whom belong to the formal sector [11]. The majority of the extremely poor are unemployed or underemployed unskilled workers, artisans and labourers who engage in stressful menial jobs for survival or are totally dependent on others. For these individuals, health care is expensive and unaffordable.

Spiritual beliefs and ignorance

There are common beliefs and practices among Africans which have been proven to be hindrances to adequate BP control. Nigerians, and indeed Africans in general, are very spiritual people, with most adopting one religion or another. Some assume health-seeking behaviour is antireligious and believe that spiritual and traditional treatments surpass orthodox medicine. As most health facilities are located in urban areas, those living in rural areas especially tend to prefer alternative medicines. These practices are more accessible to a rural population and there is a false assurance of complete healing with their use. Beyond this, ignorance and illiteracy play an important role, allowing even those who are aware of their hypertensive condition to prefer living in self-denial of the true state of their health.

Diet and drugs

Regular high consumption of salt and fat-saturated  meals, the use of substances that raise BP or oppose the antihypertensive effect of treatment (e.g., alcohol, non-steroidal anti-inflammatory drugs, some herbal remedies, or recreational drugs such as cocaine, anabolic steroids, etc.), and the use of fake, substandard or expired drugs are also reasons that hinder satisfactory BP control.

Problems of insufficient blood pressure control in Africa

Persistent insufficient BP control commonly predisposes to several cardiovascular and non-cardiovascular diseases in Nigeria and Africa as a whole. Hypertension functions through different underlying biological mechanisms for different diseases, as evidenced in a large-scale high-profile study of 1.25 million patients accruing 83,098 cardiovascular events of 12 different diseases during a median follow-up of 5.2 years. This therefore suggests that the complications of hypertension are not limited to cerebrovascular disease and myocardial infarction, commonly referred to as heart attack [12]. Other cardiovascular conditions strongly associated with hypertension in our clime are stable angina, unstable angina, heart failure, transient ischaemic attack, peripheral arterial disease, abdominal aortic aneurysm, etc. [12].

There is also clear evidence of the dual relationship between hypertension and diabetes mellitus (DM): persistent insufficient BP control has been identified as one of the strongest predictors of incident diabetes. In a large prospective cohort study of 12,550 North African adults, the development of type 2 DM was almost 2.5 times as likely in persons with hypertension (HTN) than in their normotensive counterparts [13].

Hypertension in our clinical practice, similar to findings elsewhere, has been linked with an increased risk of developing cognitive decline [14] and atrial fibrillation (AF) which is known to predispose to thromboembolic events and malignant arrhythmia [15]. Frequently, young adults (below 40 years) with sustained uncontrolled BP are seen coming down with complications such as ischaemic heart disease, intracerebral haemorrhage and heart failure which used to be commonly seen among middle-aged and elderly hypertensives.

How to ensure sustained sufficient blood pressure control in Nigeria and Africa

Blood pressure is considered controlled if systolic BP [1] is less than 140 mmHg and/or diastolic is less 90 mmHg, though newer guidelines advocate lower thresholds in certain conditions such as DM and CKD. Optimal BP control is defined as systolic less than 120 mmHg and diastolic less than 80 mmHg [3]. The Pan-African Society of Cardiology (PASCAR) recently developed a 10-point action plan for the continent aimed at achieving 25% control of hypertension by the year 2025 [16].

Regular screening programmes

Hypertension is usually asymptomatic (hence the term “silent killer”). Because of its high prevalence, more screening programmes need to be established to raise awareness about hypertension and screen all adults yearly and more frequently in people with a high to normal BP. When hypertension is suspected because of an elevated screening BP, the patient should be linked to care and the diagnosis of hypertension confirmed either by repeated office BP measurements over a number of visits or by out-of-office BP measurement using 24-hour ABPM or HBPM. The May Measurement Month programme is a great initiative in this regard with regular annual BP screening from 2017 to date [5].

Regular health education

Prevention and control of high BP through a combination of behavioural, lifestyle, and drug treatment strategies as a health system priority could mitigate the growing burden associated with high BP. Health education is of crucial importance. This can be achieved not only in the clinical setting but also using billboards, print (fliers, posters, newspapers), electronic (radio and television programmes) and even social media in order to ensure wide coverage and participation. Non-profit organisations in Africa regularly organise hypertension campaigns and screening programmes in churches, mosques, markets and other public places to improve awareness and treatment.

Part of the PASCAR strategy [16] to improve hypertension awareness, detection and control includes dialogue with key stakeholders such as traditional rulers, religious leaders, politicians and alternative medicine specialists, most of whom have significant influence in their communities. A more direct approach in Nigeria targeted at improving awareness among poorly educated market women was hugely successful with hypertension rates reducing from 21.5% to 3% while BP control rates rose dramatically from 0% to 86% within a three-month period [17].

Recommended lifestyle measures that have been shown to reduce BP are salt restriction, moderation of alcohol consumption, high consumption of vegetables and fruits, weight reduction and maintaining an ideal body weight, and regular physical activity of at least 30 minutes, three or more times a week. In addition, tobacco smoking has an acute prolonged pressor effect that may raise daytime ambulatory BP, though smoking cessation and other lifestyle measures are also important beyond BP lowering (i.e., for cardiovascular disease [CVD] and cancer prevention) [18]. The major drawback of lifestyle modification is its poor persistence over time.

Management of newly diagnosed hypertensives

This should include overall evaluation to detect CVD risk factors such as dyslipidaemia, hyperglycaemia and metabolic syndrome which frequently cluster with hypertension. The European cardiovascular disease risk assessment model, Systematic Coronary Risk Evaluation (SCORE), high-risk charts should be adapted for use in Nigeria [19]. HMOD, such as left ventricular hypertrophy (LVH), CKD or advanced retinopathy, should be dutifully screened for as well.

Reports from a randomised clinical trial have shown that early lifestyle modification is a major component for lowering systolic BP to normal levels [20]. Thus, equal and important emphasis should be placed on both lifestyle modification and medications in the control of BP. Adequate time needs to be made available during consultation to explain in detail to patients the importance of lifestyle modifications. Such interventions are important because they can delay the need for drug treatment or complement the BP-lowering effect of drug treatment.

Accessibility of quality health services for all

One of the key PASCAR action plans involves ensuring universal health access through the provision of a mandatory health insurance scheme for all citizens whether in the private or public sector [16]. Other strategies include creation and adoption of evidence-based hypertension management guidelines as well as establishment of hypertension registries which will help to monitor and report the detection, treatment and control rates of hypertension on an annual basis. Registries will also help to track patients who default on clinic attendance while also providing essential data for research [16].

Governments should also incorporate BP measurement as a prerequisite to payment of utility bills, employment, as well as renewal of vehicle documents and driving licences. Provision of digital BP machines in both public and private offices should also be mandated, in order to ensure regular BP measurement.

Non-pharmacological interventions are recommended for all adults with elevated BP or hypertension. For those requiring pharmacological therapy, the target BP should generally be less than 140 mmHg for systolic BP and/or less than 90 mmHg for diastolic BP. A regular pill count during clinic visits, a cheaper approach to detect poor or non-adherent hypertensives, is also recommended.

Conclusion

Hypertension is largely preventable, frequently asymptomatic, and often clusters with other cardiovascular risk factors such as dyslipidaemia, glucose intolerance and obesity. Healthy lifestyle changes have proven to be effective in preventing or at least delaying the development of hypertension or its complications. A holistic approach involving patients, clinicians and the government is crucial to ensure sufficient awareness, treatment, prevention and control of hypertension in sub-Saharan Africa.