Burden of Disease
Impact of Hypertension

Prepared by:

M. Mohsen Ibrahim, MD
Prof. of Cardiology – Cairo University
President of the Egyptian Hypertension Society

2003
HYPERTENSION BURDEN
HOW COMMON? MAGNITUDE OF THE PROBLEM

Global Burden

According to WHO about 15%-37% of the adult population worldwide is afflicted with hypertension. In those older than 60 years of age, as many as one-half are hypertensive in some populations. For 1990, smoking and hypertension were the major causes of global mortality. Data from World Health Report 2002 indicate that hypertension is the third most important contributor to the global disease burden. Hypertension increases the relative rate of cardiovascular events by 1.5-2.0 folds, the attributable risk in the population by 5-10%, while 5.8% of global mortality is due to hypertension.

Hypertension in Developing Countries

Very few hypertension national surveys were conducted in the developing world. Available information comes from small regional surveys which may not represent the national estimate of hypertension. Furthermore, the cut points used for definition varied from 140/90 to 160/95 mmHg. The lowest reported prevalence rates were in Ethiopian villages with a prevalence rate of 1.8% and in rural Tanzania with a rate of 2.0%. Egyptians and Caribbean have the highest hypertension prevalence rates exceeding 26% of the adult population.

Hypertension in Mediterranean Countries

Surveys in five Mediterranean countries applying the same definition of hypertension showed marked variability in prevalence rates. Only Egypt, Spain and France provided national estimates. Table (1) shows hypertension prevalence and rates of treatment and control in some Mediterranean countries

Table (1)

Egyptian National Hypertension Project

The first national hypertension survey in a developing country (1991-1994). The sample represents all Egyptian geographic and socioeconomic groups. Prevalence of hypertension increased with aging and differed between men and women. In age less than 45 years hypertension was more common in men while its prevalence was higher in women in the older age group. The highest prevalence rates were in the age decade 65-74 years where 59.4% of the population had high blood pressure, 64% in women and 54.4% in men. It was estimated that approximately 8 million Egyptians suffered from hypertension in 1991-1994. Prevalence rates in 2003 are predicted to be higher because of the aging of Egyptian population where average life expectancy increased from 51.6 years and 53.8 years for men and women respectively in 1960 to 67.5 and 71.9 years in 2002. Hypertension prevalence varied in different Egyptian regions with higher rates in urban areas. The highest prevalence rate was in Greater Cairo area (31%) while the lowest rate was in frontier regions and oasis (19.9%). Hypertension awareness rates were higher in women than men and the best hypertension control rates were reported in Egyptian coastal region while the lowest rates were in the northern parts of Upper Egypt.

Clustering of Cardiovascular Risk Factors in Hypertension

Hypertension is associated with other cardiovascular risk factors in more than 80% of hypertensive patients. Rates of diabetes, obesity, hypercholesterolemia, hypertriglyceridia and impaired glucose tolerance were higher in hypertensive patients than in individuals with normal blood pressure of the same age and gender. 10% of hypertensive Egyptian men have four or more cardiovascular risk factors.

HOW SERIOUS? HYPERTENSIVE COMPLICATIONS

Hypertension is a serious disease because if untreated leads to premature disability and mortality. As early as 1939 the rates of mortality were observed to be linearly related to the level of blood pressure. Risks of stroke are increased by 2.5-3.8 times, heart failure by 3-4 times, coronary heart disease by 2-2.2 times, and end-stage renal disease by 4.4 times.

Hypertension alone unless very high is a poor predictor of future coronary heart disease. The probability of coronary heart disease varies by 5-7 times depending upon the presence of other risk factors. Relation between mortality in men from coronary heart disease and level of systolic blood pressure varied in different countries (Seven Countries Study). At similar levels of systolic blood pressure of 160 mmHg mortality rates (per 10,000 person-year) was from 20-130.

Risks of coronary heart disease and stroke death began to increase at blood pressure levels of 125/80 mmHg and a step rise was found starting at 137/89 mmHg (MRFIT Study). Framingham Study showed that risk for coronary heart disease in men starts with systolic blood pressure levels of 120 mmHg and diastolic blood pressure levels 75 mmHg. The recent USA guidelines JNC VII labels individuals with blood pressure in the rage of 120-139/80-89 mmHg as prehypertensive and require health promoting life style modification to prevent cardiovascular disease. Starting at 115/75 mmHg, cardiovascular disease risk doubles with each increment of 20/10 mmHg throughout the blood pressure range. Data from Egyptian National Hypertension Survey shows that prevalence of target organ damage is related to the severity of hypertension as seen in table (2)

Table (2)

HOW TO MANAGE?

National guidelines for developing countries

· Hypertension guidelines from rich industrial countries may not be applicable in developing and economically disadvantaged communities.

· Poverty, high illiteracy rate, inadequate health care system with limited access to medical insurance will limit hypertensive patient's care to the minimal acceptable level rather than the ideal or optimal western care recommended in international guidelines.

· Racial, genetic, life style and environmental differences between white Caucasian and black, dark or Asian populations will influence the hypertension mechanisms, humoral profile, type and extent of complications (renal failure and stroke more common in blacks). Also, response to dietary therapy (low salt, rich fruit and vegetable diet), and antihypertensive drugs (less control with ACE-inhibitors and beta adrenergic blockers in blacks) varies.

· Risk factors for hypertension and atherosclerotic cardiovascular disease such as obesity, excess dietary salt intake, diabetes and cigarette smoking are particularly prevalent among Egyptians.

· Compared to developed countries, hypertensive population in the developing world includes a large proportion of young and middle aged individuals because of the younger mean age.

Minimal versus Optimal Care

· Resources more than science dictate the type of care that can be provided. Limited resources and economic factors will influence the level of management.

· Guidelines have to make a compromise between what is possible (minimal care) and what is ideal (optimal care). This will have an impact on evaluation (getting the required information with the least expensive methods- relying more on detailed history and physical examination) and on the initiation and type of therapy (stressing dietary therapy, life style, use of less expensive drugs, and initiating therapy at higher thresholds of blood pressure).

· Even a small reduction in blood pressure is worthwhile if absolute targets prove difficult to achieve.

Compliance

· Non compliance is probably the major cause of failure to control hypertension.

· Measures to improve compliance include patient education, use of less expensive medications, single daily dosage, fixed dose drug combination, continuous monitoring by spouse, nurse or doctor and home blood pressure self measurement.