EPIDEMIOLOGY

Hypertension Epidemiology and Cost of Illness

Dis Manage Health Outcomes 1997 Mar; 1 (3): 135- 140 1173-8790/97/0003-o135/S00.oo/0

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Helios Pardell,1,2,3 Pedro Armario,1,2 Raquel Hernandez1,2 and Ricard Tresserras2,3

1 Department of Internal Medicine, Unit of Hypertension and Cardiovascular Risk, Red Cross Hospital, Hospitalet de Llobregat, Barcelona, Spain

2 Division of Health Sciences, School of Medicine, University of Barcelona, Barcelona, Spain 3 Public Health Service, Ministry of Health and Social Security, Government of Catalonia,

Barcelona, Spain

Contents Summary ........... . .. . 1. The Impact of HypertenSion .. . 2. Questions in Hypertension Control . 3. The Cost of HypertenSion . . . . . . 4. How to Reduce the Burden of HypertenSion 5. Conclusions . . . . . . . . . . .' . . . . . . . .

135 135 137 137 138 139

Summary Hypertension is one of the most prevalent chronic conditions and a major risk factor for cardiovascular disease. Unfortunately community control of hyperten­sion remains unsatisfactory although treatment and control seems to be easy. The cost of treating hypertension is very high. It accounted for $US23.7 billion in the US (1995) and $US 1660 million in Spain (1994). It can be estimated that hyper­tension represents 5.8% of total deaths and 1.4% of total disability-adjusted life years (DALYs) worldwide. Although it is important to increase the implementa­tion of secondary prevention strategies, even increasing the direct costs, it is currently accepted that more comprehensive strategies specially focused on pri­mary prevention are needed to reduce the social impact of the burden of hyper­tension.

There are 2 pivotal ideas that clearly show the relevance of arterial hypertension in both devel­oped and developing countries. First, more than half of the US population will develop hyperten­sion during their lifetime.[l] Secondly, several epi­demiological studies have consistently identified an important and independent link between high blood pressure and various disorders, especially coronary heart disease, stroke, congestive heart failure and impaired renal functionPl

Considering the elevated economic cost of hyper­tension and its complications, it is easy to under­stand the interest in analysing the epidemiological and social consequences of this highly prevalent risk factor.

1. The Impact of HypertenSion

The relevance of arterial hypertension is sup­ported firstly by its high prevalence in almost all

136

countries worldwide, and secondly by its condition as the main cardiovascular risk factor.

Indeed, the prevalence of hypertension is very much influenced by the type of population consid­ered, the different blood pressure devices and tech­niques used, and especially by the selected blood pressure cut-off point. If the classical cut-off point (160/95mm Hg) is taken, between 8 and 18% of the population can be considered as having hyperten­sionP1

In some countries, e.g. Spain, the prevalence rate is slightly higher (around 20% in the popula­tion over 18 years))41 In several eastern European countries, higher prevalence rates (up to 30%) have been observed)51 Conversely, in some populations with primitive lifestyles, e.g. some communities of Latin America, Africa and Oceania, hypertension prevalence is much lowerP1

When the most recent cut -off point (140/90mm Hg) is used, the prevalence of hypertension in­creases and reaches levels over 30% in the adult population.[61

Hypertension prevalence increases with age and is more frequent in the US Black population and in women aged over 45 years. It appears that hyper­tension prevalence is inversely related to socio­economic status. Finally, high blood pressure shows a 'tracking' phenomenon (i.e. people with higher levels of blood pressure at baseline remain in the upper levels for life) at individual and community levels that is especially important in childhood and adolescence. [71

20 years ago, the researchers of the Framingham study[81 - which is the most important prospective study in the field of cardiovascular diseases -pointed out that the most useful single factor for detecting persons at high risk of cardiovascular dis­ease was blood pressure. This is because a large body of evidence indicates that it is the most potent precursor of cardiovascular disease, although it is not equally important for all of these diseases)81 More recently, Kannel[91 stated that approximately 35% of atherosclerotic cardiovascular events may be attributable to hypertension.

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Pardell et al.

The most relevant complications of high blood pressure are congestive heart failure, stroke, renal insufficiency, coronary heart disease and periph­eral artery disease. The associated relative risks are 2.0 for coronary heart disease, 3.8 for stroke and 4.0 for congestive heart failure)9,101

A crucial distinction between individual and community risks must be made. For individuals, the relative risk is only an expression of the risk of being exposed and assuming that the higher the blood pressure the higher the risk. Indeed, a dias­tolic blood pressure of 114mm Hg entails much more risk than one of 100mm Hg for a particular person. Conversely, at the community level the num­ber of individuals exposed to the risk is more im­portant than the blood pressure figures .

The population attributable risk is the propor­tion of disease that can be attributed to hyperten­sion i.e. the proportion of disease that could be avoided if hypertension were under control. The hypertension population attributable risk for coro­nary heart disease has been estimated as 22.7 in men.[91 Thus, mild hypertension (diastolic blood pressure 90 to 104mm Hg) entails much more at­tributable risk than severe hypertension because most patients with this condition (about 75%) have only mild hypertension.

The increase of risk is associated with both sys­tolic and diastolic blood pressure. Cardiovascular risk increases dramatically when hypertension co­incides with other cardiovascular risk factors in the same individual. This is not rare in practice (around 20% of hypertensives are smokers or have hyper­cholesterolaemia).[111

In the Multiple Risk Factor Intervention Trial, the risk of those individuals in the higher quintile for blood pressure and blood cholesterol who were smokers was 20-fold more than that observed in nonsmokers in the lowest blood pressure and blood cholesterol quintiles. [121

The impact of hypertension at the community level is enormous, constituting one of the most rel­evant public health problems in many countries. In the context of the Global Burden of Disease Study, Murray and Lopez[ 131 have estimated that hyper-

Dis Manage Health Outcomes 1997 Mar; 1 (3)

Hypertension: Epidemiology and Cost of Illness 137

Table I. The global burden 01 disease and injury attributable to selected risk factors in 1990 (reproduced from Murray et al .,1131 with permission)

Risk factor Deaths (x1oJ) Total deaths (%) DALYs (x106) Total DALYs

Malnutrition 5881 11.7 219.6 15.6

Poor water supply, sanitation and hygiene 2668

Unsafe sex 1095

Tobacco use 3038 Alcohol use n4 Occupation 1129

Hypertension 2918

Physical inactivity 1991

Illicit drugs use 100

Air pollution 568

Abbreviation: DALY = disability-adjusted life year.

tension is responsible for about 2918000 annual deaths worldwide, which equates to 5.8% of total deaths (table 1).[13)

2. Questions in Hypertension Control

The situation reported in section 1 could still be more worrying because in many countries less than 20% of people with hypertension have a blood pressure below 160/95mm Hg.ll4) Also, even worse, if we adopt the most recent and restric­tive criteria of hypertension control (blood pres­sure < 140/90mm Hg) that proportion is substan­tially lower.

Surprisingly, although hypertension is a condi­tion which is easy to diagnose, it often remains undetected. Also, although it may be simple to treat, this condition very often remains untreated. Despite the availability of nonpharmacological measures and potent medications, treatment is too often ineffective in practice (Strasser's triple para­dOX).[15)

During recent years, hypertension control in the community has been widely analysed. At the World Conference on Hypertension Control held in Ot­tawa, Canada, in 1995, the most relevant problems in achieving significant hypertension control lev­els in the community were deeply analysed.l l6) Ac­cording to the opinions of the experts, the more important barriers to reaching optimal community control levels are economic and cultural factors and those arising from the chronic condition ofhy-

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5.3 93.4 6.8

2.2 48.7 3.5

6.0 36.2 2.6

1.5 47.7 3.5

2.2 37.9 2.7

5.8 19.1 1.4

3.9 13.7 1.0

0.2 8.5 0.6

1.1 7.3 0.5

pertension.£l7-19) This point is especially important as approximately 40 to 50% of treated patients with hypertension do not adequately comply with the physicians' prescriptions(20) and, for several rea­sons closely related to the management of patients with hypertension, the overall outcomes for a group of patients with hypertension could be im­proved if compliance etc. were improved.[2I)

An important portion of the benefits that can be expected, can only be obtained if hypertension re­mains under control. The lack of this control ac­counts for a large number of deaths and disabilities which could really be avoided.

3. The Cost of Hypertension

As a consequence of the high prevalence and the associated fatal and nonfatal complications rate, hypertension implies a great economical and social cost. Because of this, hypertension is a leading target for the experts in health economy and cost­benefit analysis.£22)

According to the US National Heart, Lung, and Blood Institute, hypertension cost $US 18.3 billion in the US in 1990. 69% of that cost was for direct health expenditure (hospital, physician, drug and nursing home charges) and 31 % for indirect costs in lost wages and lowered productivity.(23) In 1995, the estimated cost of hypertension was US$23.74 billion (US$17.07 billion in direct costs and $US6.67 billion in indirect costs).[24) However, these estimations are very conservative because

Dis Manage Health Outcomes 1997 Mar; 1 (3)

138

they are only based on hypertension treatment costs and exclude the costs of treating hypertension­related complications.

In the US, it has been possible to estimate that hypertension alone, increases the Medicare Costs by $US527 per elderly person per year, and that the com­bination of hypertension, smoking and hyperchol­esterolaemia increases that cost by $US1757J25]

In 1985 in Spain, it was estimated that the hyper­tension cost was $US830 million, which accounted for 3% of the national health expenditure in that year.[26] Direct costs represented 40% while indi­rect costs constituted 60% (table II). It was esti­mated that in 1985 hypertension was responsible for 50 000 years of potential life lost in the popu­lation aged <65 years. In a recent update, the total cost for 1994 was estimated as $US1660 million.l27]

Although comparisons of indirect costs are dif­ficult because of calculation methodological com­plexities,[28] table I provides an overview of the significance of indirect costs of hypertension world­wide. It has been estimated that hypertension ac­counts for 19 100 disability-adjusted life years (DALYs) worldwide, i.e. 1.4% of the total DALYs.[13]

Inversely, direct costs are easy to estimate and consequently comparisons are more feasible (table III). There are important differences among coun­tries, for example in Finland, Sweden and Spain, differences can be observed according to the inten­sity of the interventions.

Table II. Cost of hypertension in Spain (1985) [reproduced from Badia et al.[23,]

Concept

Primary healthcare

Hospital care

Pharmacy

Total direct cost

Attributable mortality

Attributable morbidity

Disability

Total indirect cost

Total cost

Cost (millions $US)"

219

78

110

407

317

8

194

519

926

a Amounts have been calculated taking an exchange rate of $US1 = 120 pesetas.

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Pardell et al.

Table III. Direct costs of hypertension in selected countries

Country Year Cost (millions Cost per person $US per year) ($US per year)

Finland 1972-77" 4.5 26.2 (North Karelia)

Sweden

Spain

1988

1985

153.0

489.0

18.3

12.7

a Population younger than 66 years.

Medication largely contributes to the increase in hypertension-related cost. Menard et al.[29] calcu­lated that in France antihypertensive drugs expen­diture has increased from F486.1 million in 1970 to F5063 million in 1990 (lO.4-fold increase), while in the same period, total medication expen­diture only increased 1.94-fold.

All these estimates must be underestimates be­cause the real cost of hypertension is much bigger in the real world. When considering the true cost, a major fraction of the cost of heart disease and stroke should be included, and these are actually huge.[29.30]

4. How to Reduce the Burden of Hypertension

It is very well known that important benefits can be expected if hypertension is adequately treated. It has been estimated in the US, that by reducing blood pressure in 3.6 million people with hyperten­sion from a range of 100 to 104mm Hg to 95mm Hg or lower, about 12000 deaths could be pre­vented annually. This would represent a reduction of about $US 1 billion of the national health expen­di ture.l3 I]

Although treating people with hypertension and doing it more intensively will result in an increase in direct costs, if the intervention is effective, it will curtail the indirect costs. As a result, the final bal­ance in terms of avoiding social cost is very posi­tive. (fig. 1). For this reason, and according to the last WHO Expert Committee Report,[2] early iden­tification and effective management of individuals with hypertension should be promoted. In addition, the effective management of patients with hyper-

Dis Monage Health Outcomes 1997 Mar: 1 (3)

Hypertension: Epidemiology and Cost of Illness

tension should consider the new approaches mainly focused on the individualised regimesP21

Therefore, the main emphasis is centred on achieving the optimal control level in each com­munity, as it was recommended in the World Con­ference on Hypertension Control. Education of healthcare professionals, patients and the general population is crucial for the success of the high blood pressure control programmes. Furthermore, secondary prevention approach is not fully satis­factory. Lenfant[331 recently stated that there is am­ple evidence that current approaches are less than optimal.

Despite the considerable efforts made to im­prove hypertension control, the incidence and prevalence of high blood pressure have not shown any tendency to decline over decades of follow-up of the Framingham cohort.l341 Hence, as it is stated in the last WHO Expert Committee Report, pre­vention of hypertension by measures aimed at re­ducing the blood pressure levels in the population as a whole should be considered as a fundamental component of a comprehensive strategy to prevent the hypertension-associated complications,l21

Since the association of hypertension with other cardiovascular risk factors increases the final risk, the implementation of integrated programmes will also entail the optimum community benefitsp51

Today, primary prevention of hypertension of­fers great opportunities with many successful ex­periences in different countries.[361 In fact, this is

Treated HT

Nontreated HT I

o Direct cost

o Indirect cost

I J Benefits . ~

I Fig. 1. Cost of treated and non·treated hypertension (HT). Ex· pected benefits from treatment.

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139

the only way to achieve the reduction of the bur­den, lowering the health cost by reducing the need and demand for medical services.l371

5. Conclusions

Hypertension is highly prevalent in most devel­oped and developing countries and it accounts for more than 35% of total cardiovascular events. Al­though it is an easy condition to diagnose and treat, the hypertension control level in the community is really deficient.

The cost of hypertension is very high, account­ing for around 3% of global health expenditure in some countries. Interventions aimed at reducing the incidence and prevalence of hypertension are needed. This is the only realistic approach to low­ering the cost of the burden.

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About the Author: Dr Helios Pardell is currently Professor of Medicine at the University of Barcelona, Head of the In­ternal Medicine Department at the Red Cross Hospital in Hospitalet de L10bregat (Barcelona) and Executive Director of the CINDI Programme in Catalonia, Spain. His profes­sional and research interests are mainly focused on epide­miology of hypertension and other cardiovascular risk factors and on intervention programmes at clinical and community levels. Correspondence and reprints: Dr H. Pardell, Department of Internal Medicine, Unit of Hypertension and Cardiovas­cular Risk, Red Cross Hospital, Av. Jose Molins, 29-41, 08906 Hospitalet de L1obregat, Barcelona, Spain.

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