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Advanced Neurology Stroke care in sub-Sahara Africa

eastern regions was observed, while the risk was lower in 3.3.2. Modifiable risk factors
southern SSA. 33 Potential major modifiable stroke risk factors primarily
Several studies from SSA have identified key stroke risk include traditional cardiometabolic disorders such as
factors categorized here as modifiable and non-modifiable hypertension, diabetes mellitus, dyslipidemia, active
factors. tobacco use, and cardiac diseases (atrial fibrillation,
cardiomyopathy with reduced ejection fraction, ischemic
3.3.1. Non-modifiable risk factors heart disease with associated wall motion abnormalities,
The age factor serves as an independent, non-modifiable large patent foramen ovale, cardiac thrombosis, and
risk factor for stroke. Multiple epidemiological studies have infective endocarditis). 39,44 Additional risk factors include
established that stroke risk increases with age. However, smoking, obesity, obstructive sleep apnea, physical
several studies from SSA have indicated that stroke tends inactivity, excessive alcohol consumption, and diet.
to occur at a much younger age compared to studies from The INTERSTATE study, a case–control study that
Western countries. A prospective cohort study from the recruited participants from 84 centers in 22 countries,
United Kingdom reported a mean age at incident stroke including four countries from SSA (Mozambique,
of 74 years, which is higher than the mean age reported Nigeria, South Africa, and Uganda), assessed known and
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by multiple studies in SSA, ranging between 59 and emerging stroke risk factors, their primary subtypes, and
68 years. 35-38 Indeed, the Stroke Investigative Research and their contributions to the burden of stroke. Collectively,
Education Network (SIREN) study, a multicenter case– 10 risk factors were identified (hypertension, current
control study conducted in Nigeria and Ghana, showed smoking, diabetes mellitus, cardiac diseases, waist-to-hip
that up to 24% of enrolled stroke cases occurred in patients ratio, physical inactivity, alcohol intake, psychological
less than 50 years old. 39 stress, depression, and apolipoproteins B/A ratio) and
Genetic risk factors are emerging as significant non- accounted for 88.1% of the population attributable risk for
modifiable risk factors. Candidate genes shown to be all strokes. The three major modifiable stroke risk factors
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associated with the risk of stroke in the African population for SSA countries that participated in the INTERSTATE
include IL6, APOE, APOL1, CYB11B2, and CDKN2A/2B. study were hypertension (odds ratio [OR]: 4.96, 95%
However, the unique role and extent of attributable risk in confidence interval [CI]: 3.11 – 7.91), current smoking
this population remain to be clearly defined. (OR: 2.18, 95% CI: 1.07 – 4.43), and waist-to-hip ratio (OR:
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Sickle cell disease (SCD) is an inherited autosomal 1.73, 95% CI: 0.99 – 3.02). Similarly, the SIREN study
recessive disorder arising from a single point mutation in identified six common modifiable risk factors associated
the b-globin gene. Although SCD occurs globally, the SSA with stroke, including hypertension (88.7%), dyslipidemia
region has the highest prevalence of the disease. Of the (48.2%), diabetes mellitus (22.6%), low green vegetable
estimated 4.4 million people worldwide with SCD, close to consumption (18.2%), psychosocial stress (14.5%), and
80% are in SSA, with a mortality rate for children under cardiac disease (8.4%).
five years old ranging from 50 to 80%. A systematic review Socioeconomic and cultural transitions are changing
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and meta-analysis involving 18,977 participants with SCD stroke risk profiles in SSA. The adoption of more Western
pooled from 23 African studies showed an overall prevalence practices in Africa, such as higher consumption of
of stroke of 4.2%. The Sickle Pan African Research processed foods and increased tobacco use, is presumed
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Consortium (SPARCO) study, using an electronic database to contribute to the observed high burden of modifiable
of patients with SCD from 20 SPARCO collaborative centers stroke risk factors and the changing dynamics of stroke
in Nigeria, reported a lower frequency of stroke at 2.5%. risk factors in this region. Additional contributors
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In addition, a hospital-based retrospective study found a include rural-to-urban migration coupled with sedentary
stroke frequency of 5.4% with a mean age of incident stroke lifestyles. A comparative study of racial disparity in stroke
of 6.8 years. Clinical manifestations of SCD are manifold. risk factors between indigenous Africans in Ibadan,
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However, the basic pathophysiologic mechanisms that Nigeria, and Berlin, Germany, found a higher frequency
explain SCD complications, including stroke, are the same. of hypertension but slightly lower frequency of diabetes
The polymerization of abnormal hemoglobin causes the mellitus and current smoking in Africans compared to
deformation of the red blood cells into a characteristic rigid Germans. Figure 2 shows that hypertension remains
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sickle shape, which adheres to the microvasculature within pervasive and is the major modifiable risk factor for
tissues and organs. This process then triggers a myriad of stroke in SSA. However, other vascular (cardiac diseases,
cellular events that culminate in vaso-occlusion, ischemia, smoking, and dyslipidemia) and non-vascular (infection,
and organ or tissue infarctions. alcohol consumption, physical inactivity, obesity, and

Volume 3 Issue 2 (2024) 5 doi: 10.36922/an.2804