HYPERTENSION BURDEN AND CVD
RISK PREDICTION IN AFRICA
Projected global deaths by cause (in millions), 2005
0,883
Malaria
1,125
Diabetes
1,607
Tuberculosis
WHO Report 2005
2,83
HIV/AIDS
4,057
Chr Resp Dse
7,586
Cancer
17,528
CVD
0
5
10
15
20
Global Cardiovascular Disease Burden
17 million global deaths due to CVD
¾ in Developing Countries
Projected death rates by specific causes
for selected countries, all ages, 2005
Age-standardized death rates per 100,000
HIV/AIDS, TB, Malaria
CVD
800
700
600
500
400
300
200
100
0
Tanzania
Nigeria
India
WHO Report 2005
China
UK
Challenge of CVD in Africa
• Double burden of disease
• Changing pattern of disease and risk factor
exposure
• Infectious disease priorities; constrained
budgets
• Focus on population approaches to
prevention
• Standard surveillance of major risk factors
Challenge of CVD in Africa
• Prevention and surveillance are
particulaly relevant in Africa:
• In SSA, the need for appropriate care for
CVD will place an enormous pressure on
the already fragile health care systems
and jeopardize the viability of poorly
funded public health services
• Cost-effective strategies are needed and
prevention strategies are therefore
particularly relevant in resource-poor SSA
countries
.
WHO Regions
Disease burden (DALYs) in 2000 attributable to selected leading risk
factors
Blood
pressure
Number of Disability-Adjusted Life Years (000s)
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
AFRO AMRO EMRO EURO SEARO WPRO
EPIDEMIOLOGY of HYPERTENSION
in Africa
Projections for 2025 based on the assumption that country
specific prevalence estimates will remain constant!!!!
Rate of HBP, 2000 - 2025
We are 79.8
Number of people with HBP, 2000 - 2025
M and we will be 150.9 M by 2025
Lancet 2005; 365: 217–23
WHO Regions
Deaths in 2000 attributable to selected leading risk factors
2500
2434
2000
Number of deaths (000s)
Blood
pressure
1500
1630
1459
1000
742
500
468
410
0
AFR
AMR
EMR
EUR
SEAR
WPR
Diseases Attributable to Hypertension
Heart Left Ventricular
Gangrene of the
Failure Hypertrophy Myocardial
Lower Extremities
Infarction
Hypertensive
Encephalopathy
Aortic
Aneurym
HYPERTENSION
Blindness
Coronary
Heart Disease
Cerebral
Chronic
Stroke Preeclampsia/ Hemorrhage
Kidney
Eclampsia
Failure
Adapted from Dustan HP et al. Arch Intern Med. 1996; 156: 1926-1935
HYPERTENSION BURDEN IN
Africa

Stroke is a major complication of Hypertension in Africa
Lemogoum et al, Am J Prev Med 2005;29 (5SI):95-101

Stroke mortality and case fatality in some Africa
countries exceed those in the developed world
Walker et al, Lancet 2000;355:1684-87

Hypertension is the most consistent and powerful
predictor of stroke and is causally involved in more
than 70% of stroke cases
Lavados et al, Lancet 2005; 365:2206-15. Bronner et al, N Engl J Med 1995;333: 1392-400
Stroke mortality by region (1990)
Mortality rate
(per 100,000)
Former socialist economies
China
Established market economies*
Sub-Saharan Africa
India
Middle Eastern Crescent
Other Asian countries and islands
Latin America
192.35
112.12
98.02
76.25
72.89
65.08
51.34
28.49
*Western Europe, USA, Canada, Australia,
New Zealand, Japan
Adapted from Reddy KS, Yusuf S. Circulation 1998;97:596-601
Risk of AMI in African region: INTERHEART

578 cases and 789 controls, 9 SSA countries

Blacks (36.3%), Coloured (46.7%),
European/Other (17%)

67% of AMI were men

Mean ages: Men 53.2 ± 11.6 yrs; Women 56.4 ±
11.0 yrs

Similar relationships between the common CVD
risk factors and AMI as found in the overall
INTERHEART Study

Hypertension, Diabetes, Smoking, abdominal
obesity and abnormal apoB/ApoA1 ratio
provided a PAR of 89.2% for AMI
Steyn K et al. INTERHEART AFRICA Study. Circulation 2005; 112(23):3554-61
SINGLE RISK FACTOR APPROACH
Is it necessary to change paradigm?
• Clustering of three major risk factors
• Other risk factors
• Close association between CVD and
diabetes
• Importance of BP control for outcomes
in diabetes
• Hypertension or diabetes as entry
points
• Pragmatism, PHC, health workers
• Science (cost effectiveness)
Obesity: Urban-Rural Population,
Cameroon
28
BMI (Kg/m²)
76
Weight (Kg)
78
29
74
72
77.4
70
106
104
102
106.0
98
94
26.2
98.3
P <0.001
30
25
20
15
10
30.3
18.1
5
0
100
P <0.001
Waist Circumference (cm)
Hip Circumference (cm)
108
96
26
28.5
24
66
100
27
25
70.4
68
35
P <0.001
Obesity (BMI >=30kg/m²)
30
P <0.001
80
P <0.001
98
Urban Population
96
94
Rural Population
92
90
96.7
88
86
84
88.7
Hypertension Prevalence according to Obesity in
Cameroon
P <0.001
P <0.001
50
40
30
48.4
20
10
32.7
24.7
34.1
0
1
2
3
4
Arterial Hypertension (%)
Arterial Hypertension (%)
60
50
45
40
35
30
25
20
15
10
5
0
40.2
31.7
19.7
1
2
BMI quartiles*
*
1st
2nd
3rd
4th
< 21.5 kg/m²
21.6-24.2 kg/m²
24.3-25.7 kg/m²
>25.8 kg/m²
45.8
3
4
Waist / Hip quartiles**
**
1st
2nd
3rd
4th
< 0.86
0.87-0.91
0.92-0.97
>0.98
Arterial Hypertension : Antihypertensive treatment or screening SBP>= 140 mmHg and/or DBP>=90mmHg
Projections for the Diabetes
Epidemic: 2003-2025
Global
SSA
Prevalence of Diabetes: Urban-Rural Population
in Cameroon
P <0.05
12
10
Urban Population
Rural Population
6
11.0
4
5.9
Television Frequency
2
45
0
P <0.001
40
35
30
Diabetes: IDF definition
%
Diabetes (%)
8
25
41.4
20
15
20.9
10
5
21.6
6.4
0
Never
Always
MULTIFACTORIAL RISK APPROACH
• Risk is multifactorial.
• Absolute CVD risk of any one risk factor is determined
by the multiplicative effects (total risk) of the other
concomitant risk factors.
• Therefore the intensity of the prevention strategy
should be guided by level of absolute multifactorial or
total risk.
What is my patients total (multifactorial) risk of developing
heart attack or stroke?
Probabilité d’accident
10-Années %
Impact of multiples risk factors on the probability
of Coronary Heart Disease: Framingham study
SBP
Cholesterol
HDL-C
Diabetes
Cigarettes
ECG-LVH
40
42
36
30
24
18
12
6
0
150-160
240-262
33-35
21
14
10
6
4
+
-
+
+
-
Kannel. Am J Hypertens. 2000;13:3S-10S.
+
+
+
-
+
+
+
+
-
+
+
+
+
+
-
+
+
+
+
+
+
Strategies for prevention
 Reducing risk factor availability (primordial
prevention)
 Reducing prevalence of risk factor
exposure (primary prevention)
 Limiting the complications of established
CVD (secondary prevention)
 Only the population strategy is feasible –
requires commitment of policy makers
Population based approaches
Very cost effective
Policies for promotion of
• Tobacco control
• Healthy Diet
• Physical activity
Primary Prevention Interventions
with Proven Efficacy
• Weight Loss
• Exercise
• Reduced Sodium Intake
• Reduced Alcohol Consumption
Population-Based Strategy
SBP Distributions
Before
Intervention
After
Intervention
Reduction
in BP
Reduction in SBP
mmHg
2
3
5
% Reduction in Mortality
Stroke CHD
Total
-6
-8
-14
-4
-5
-9
-3
-4
-7
Hypertension 1991;17(Sup):16–20.