HYPERTENSION BURDEN AND CVD RISK PREDICTION IN AFRICA

Projected global deaths by cause (in millions), 2005

17,528

7,586

4,057

2,83

1,607

1,125

0,883

0 5 10 15 20

CVD

Cancer

Chr Resp Dse

HIV/AIDS

Tuberculosis

Diabetes

Malaria

WHO Report 2005

Global Cardiovascular Disease Burden

17 million global deaths due to CVD

¾ in Developing Countries

0

100

200

300

400

500

600

700

800

Tanzania Nigeria India China UK

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HIV/AIDS, TB, Malaria CVD

Projected death rates by specific causes for selected countries, all ages, 2005

WHO Report 2005

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

.

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

AFRO AMRO EMRO EURO SEARO WPRO

Bloodpressure

WHO RegionsDisease burden (DALYs) in 2000 attributable to selected leading risk

factors

Num

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abili

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Life

Yea

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00s)

Lancet 2005; 365: 217–23

Rate of HBP, 2000 - 2025 Number of people with HBP, 2000 - 2025

We are 79.8 M and we will be 150.9 M by 2025

Projections for 2025 based on the assumption that country specific prevalence estimates will remain constant!!!!

EPIDEMIOLOGY of HYPERTENSION in Africa

410

742

468

2434

1459

1630

0

500

1000

1500

2000

2500

AFR AMR EMR EUR SEAR WPR

Bloodpressure

WHO RegionsDeaths in 2000 attributable to selected leading risk factors

Num

ber o

f dea

ths

(000

s)

Diseases Attributable to HypertensionDiseases Attributable to Hypertension

HYPERTENSION

Gangrene of the Lower Extremities

Heart Failure

Left Ventricular Hypertrophy Myocardial

Infarction

Hypertensive Encephalopathy

Aortic Aneurym

Blindness

Chronic Kidney Failure

Stroke Preeclampsia/Eclampsia

Cerebral Hemorrhage

Coronary Heart Disease

Adapted from Dustan HP et al. Arch Intern Med. 1996; 156: 1926-1935

HYPERTENSION BURDEN IN HYPERTENSION BURDEN IN AfricaAfrica

Stroke is a major complication of Hypertension in Africa Stroke is a major complication of Hypertension in Africa Lemogoum et al, Am J Prev Med 2005;29 (5SI):95-101 Lemogoum et al, Am J Prev Med 2005;29 (5SI):95-101

Stroke mortality and case fatality in some Africa Stroke mortality and case fatality in some Africa countries exceed those in the developed worldcountries exceed those in the developed world

Walker et al, Lancet 2000;355:1684-87Walker et al, Lancet 2000;355:1684-87

Hypertension is the most consistent and powerful Hypertension is the most consistent and powerful predictor of stroke and is causally involved in more predictor of stroke and is causally involved in more than 70% of stroke casesthan 70% of stroke cases Lavados et al, Lancet 2005; 365:2206-15. Bronner et al, N Engl J Med 1995;333: 1392-400Lavados et al, Lancet 2005; 365:2206-15. Bronner et al, N Engl J Med 1995;333: 1392-400

Stroke mortality by region (1990)Stroke mortality by region (1990) Mortality rateMortality rate (per 100,000)(per 100,000)

Former socialist economiesFormer socialist economies 192.35192.35ChinaChina 112.12112.12Established market economiesEstablished market economies** 98.02 98.02Sub-Saharan AfricaSub-Saharan Africa 76.25 76.25IndiaIndia 72.89 72.89Middle Eastern CrescentMiddle Eastern Crescent 65.08 65.08Other Asian countries and islandsOther Asian countries and islands 51.34 51.34Latin AmericaLatin America 28.49 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: INTERHEARTRisk of AMI in African region: INTERHEART

578 cases and 789 controls, 9 SSA countries 578 cases and 789 controls, 9 SSA countries

Blacks (36.3%), Coloured (46.7%), Blacks (36.3%), Coloured (46.7%), European/Other (17%)European/Other (17%)

67% of AMI were men67% of AMI were men

Mean ages: Men 53.2 ± 11.6 yrs; Women 56.4 ± Mean ages: Men 53.2 ± 11.6 yrs; Women 56.4 ± 11.0 yrs11.0 yrs

Similar relationships between the common CVD Similar relationships between the common CVD risk factors and AMI as found in the overall risk factors and AMI as found in the overall INTERHEART StudyINTERHEART Study

HypertensionHypertension, , Diabetes, Smoking, abdominal Diabetes, Smoking, abdominal obesity and abnormal apoB/ApoA1 ratio obesity and abnormal apoB/ApoA1 ratio provided a PAR of 89.2% for AMIprovided a PAR of 89.2% for AMI

Steyn K et al. INTERHEART AFRICA Study. Circulation 2005; 112(23):3554-61

SINGLE RISK FACTOR APPROACHIs 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)

P <0.001 P <0.001

P <0.001 P <0.001

P <0.001

Urban Population

Rural Population

Obesity: Urban-Rural Population, Obesity: Urban-Rural Population, CameroonCameroon

30.3

18.1

P <0.001 P <0.001

** 1st < 0.86 2nd 0.87-0.91 3rd 0.92-0.97 4th >0.98

* 1st < 21.5 kg/m² 2nd 21.6-24.2 kg/m² 3rd 24.3-25.7 kg/m² 4th >25.8 kg/m²

Arterial Hypertension : Antihypertensive treatment or screening SBP>= 140 mmHg and/or DBP>=90mmHg

Hypertension Prevalence according to Obesity in Hypertension Prevalence according to Obesity in CameroonCameroon

Projections for the Diabetes Projections for the Diabetes Epidemic: 2003-2025Epidemic: 2003-2025

Global

SSA

Prevalence of Diabetes: Urban-Rural Population Prevalence of Diabetes: Urban-Rural Population in Cameroonin Cameroon

P <0.05

P <0.001

Never Always

Television Frequency

Urban Population

Rural Population

Diabetes: IDF definition

MULTIFACTORIAL RISK APPROACH 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?

• 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?

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36

42

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SBPSBP 150-160150-160 ++ ++ ++ ++ ++ ++CholesterolCholesterol 240-262240-262 -- ++ ++ ++ ++ ++HDL-CHDL-C 33-3533-35 -- -- ++ ++ ++ ++DiabetesDiabetes -- -- -- ++ ++ ++CigarettesCigarettes -- -- -- -- ++ ++ECG-LVHECG-LVH -- -- -- -- -- ++

44 661010

1414

2121

4040

Kannel. Am J Hypertens. 2000;13:3S-10S.Kannel. Am J Hypertens. 2000;13:3S-10S.

Impact of multiples risk factors on the probability of Coronary Heart Disease: Framingham study

Strategies for preventionStrategies for prevention

Reducing risk factor availability (primordial Reducing risk factor availability (primordial prevention)prevention)

Reducing prevalence of risk factor Reducing prevalence of risk factor exposure (primary prevention)exposure (primary prevention)

Limiting the complications of established Limiting the complications of established CVD (secondary prevention)CVD (secondary prevention)

Only the population strategy is feasible – Only the population strategy is feasible – requires commitment of policy makersrequires 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 StrategyPopulation-Based Strategy

Hypertension 1991;17(Sup):16–20.Hypertension 1991;17(Sup):16–20.

Reduction in SBPmmHg

2

3

5

% Reduction in Mortality

Reduction in BP

Reduction in BP

After InterventionAfter Intervention

Before Intervention

Before Intervention

Stroke CHD Total

-6 -4 -3

-8 -5 -4

-14 -9 -7

SBP Distributions