Chapter 1: Introduction

 1.1. Background

Low and middle income countries have the largest burden of stroke, accounting for more than 85% of stroke mortality worldwide yet data on risk factors for stroke are scarce (1). In Cameroon stroke is the fourth leading cause of death with a prevalence of 7.3%(2).Stroke is defined as rapidly developing clinical signs of focal or global disturbance of cerebral function, lasting more than 24hrs or leading to death, with no apparent cause other than that of vascular origin (3). Risk factors for stroke can be categorized as modifiable and non- modifiable. Age, sex and race/ethnicity are non- modifiable risk factors, while hypertension, smoking, diet, and physical inactivity are among some of the more commonly reported modifiable risk factors. More recently described risk factors and triggers of stroke include inflammatory disorders, infection, pollution  and cardiac atrial disorders independent of atrial fibrillation (4). The modifiable risk factors are of utmost importance, as intervention strategies aimed at reducing these factors can subsequently reduce the risk of stroke. Early identification and modification of these risk factors is imperative (4).

The burden of stroke is a major public health issue of growing importance (5). In 2019, there were 12.2 million incident cases of stroke, 101 million prevalent cases of stroke, 143 million DALYs due to stroke and 6.6 million deaths from stroke. During the past three decades, global stroke incidence increased by 70%, its prevalence increased by 85%, its mortality increased by 43% and DALYs as a result of stroke increased by 32%, with a greater increase in the burden of stroke in low and middle income countries than in high income countries (6). From 1990 to 2019, there was a 37% global increase in the total number of stroke-related DALYs due to risk factors, with LMICs affected disproportionately. Stroke related DALYs attributed to risk factors increased by 48% in LMICs and declined by 25%in HICs in the last 3 decades. In 2019, the five leading risk factors were high systolic blood pressure, high BMI, high fasting plasma glucose concentrations, pollution and smoking (6). These results were however inconsistent with a study carried out in Jiangxi  China where physical inactivity rather than hypertension was identified as the most important risk factor, indicating that the priority of risk factors in different regions may be different (7).

Stroke is the leading cause of long-term disability and the second most common cause of death worldwide (8). Low and middle income countries have the largest burden of stroke, accounting for more than 85% of stroke mortality worldwide, but  data  available to identify risk factors for stroke in most of these regions and particularly for hemorrhagic stroke are scarce (1).

Global estimates of stroke burden suggest that Sub-Saharan Africa has the highest incidence (age standardized incidence of 316 per 100000 people per year), prevalence (age-adjusted prevalence of up to 14.6 per 1000 people), and case fatality (up to 43% at 1 month and 84% at 3 years) as compared to the developed world (6). Over the last two decades, there has been modifications of the disease epidemiology in Sub-Saharan Africa with emergence of non-communicable chronic diseases like hypertension, diabetes mellitus, dyslipidemia and obesity. Aging of the population, economic status and modifications of lifestyle have been observed with increasing sedentary tendencies, alcohol consumption and tobacco smoking. All these conditions are prone to increase the incidence of stroke in this part of the world (9).

INTERSTROKE, the largest case-control study on stroke so far, reported regional differences in stroke types and leading risk factors globally (8). However, no significant association was found between stroke and important risk factors such as diabetes, cigarette smoking, physical inactivity, dietary and psychosocial factors among Africans, probably because of the small number of Africans in the study (1). This may be different in our setting given the possible differences in clinical characteristics, economic status and lifestyle of the population.

The global burden of disease (GBD) study showed regional variation in risk factors for stroke worldwide and explored risk factors for stroke among Africans using a meta-analysis of the small amount of data available (6).

In Cameroon, the prevalence of stroke is 7.3% (2) and its mortality rates are 26.7% during the first month and 31.7% in the first 3 months after the stroke with an increased prevalence of recurrence which is associated with multiple modifiable risk factors (10,11) . The total direct annual medical cost of stroke is XAF 295,662,600 and XAF 157,370,700 for ischemic and hemorrhagic strokes respectively (12). Despite the treatment cost, intra-hospital stroke mortality remains high in Cameroon(13). Mortality from stroke in people living with HIV in Yaoundé was found to be high and implied the need to improve stroke prevention and management of these patients.                                                                    

1.2. Problem Statement.

There is  increasing incidence, prevalence and case fatality of stroke in Sub-Saharan Africa with regional variation in risk factors (1). In Cameroon, stroke is the fourth leading cause of death (14) but there are few studies on the risk factors for stroke and most are related to specific conditions (15). Mortality and disability of stroke are high in our setting (16), but information about the     magnitude of the risk factors  are unknown .

1.3. Rationale

 Few studies carried out in Cameroon and Bamenda have shown the most prevalent risk factors for stroke.  However, some of the risk factors described out of Cameroon were not included in these studies and the extent to which the risk factors investigated affected the population were not determined. Given the regional variation in the risk factors for stroke globally, the increasing number of cases, poor quality of health care and life style of the population of Bamenda, prevention may be the most effective way to reduce the burden of stroke. Therefore, it is necessary to identify and quantify the common risk factors for stroke at the Bamenda Regional Hospital.

1.4. Research Question

1. a) To what extent do individual cerebrovascular risk factors contribute to the burden of stroke at the Bamenda Regional Hospital?

1.5. Objectives

General Objective; To ascertain the contribution of risk factors for stroke to the stroke burden at the Bamenda Regional Hospital.

Specific Objectives

1) To identify the cerebrovascular risk factors for stroke in this population

2) To identify lifestyle factors associated with stroke in the control group

3) To describe the clinical features of stroke in this population