Hypertension worldwide

Social and cultural differences affect risk factors for cardiovascular diseases

Countries vary widely in their capacity to manage hypertension, but globally the majority of diagnosed hypertensives is inadequately controlled. Not treated it can cause cardiovascular disease (CVD), myocardial infarction and stroke. According to the WHO, hypertension is estimated to cause 4.5% of the current global disease burden and is as prevalent in many developing countries as in the developed world. Here, three experts from three continents comment on risk factors and hypertension management in their countries.

Dr Fiona Turnbull, George Institute for International Health, University of...
Dr Fiona Turnbull, George Institute for International Health, University of Sydney, Australia

Blood pressure-related disease is a major global health problem and is responsible for nearly eight million deaths annually. About half of all stroke and coronary heart disease is attributable to non-optimal blood pressure (BP). Furthermore, about 50% of these major cardiovascular events occur in people who are so-called ‘normotensive’. Therefore major health gains can be achieved by lowering BP, even in people who are not hypertensive according to traditional threshold values. Obviously obesity and nutritional factors, especially salt consumption, play a major role in blood pressure. With the rapid epidemiological transition occurring in low-middle incomes, such as China and India, CVD attributable to BP is becoming increasingly prevalent in developing as well as developed countries.
Although lifestyle factors are important, drug therapy remains the mainstay of blood pressure control and, given the millions of people increasingly prescribed therapy, it is critical to be able to discern even small differences in the benefits of different drug classes.
A major component of my activities has been the leadership since 2003 of the Blood Pressure Lowering Treatment Trialists’ Collaboration (BPLTTC). This is an international collaboration of the principal investigators of major trials of blood pressure-lowering regimens. The collaboration seeks to provide clinicians, patients and policy-makers with the most reliable information about BP drugs and their effects on major cardiovascular events, such as stroke and coronary heart disease, by conducting meta-analyses (pooled analyses) of these trials.
The work of the Collaboration is conducted at the George Institute for International Health in Sydney, Australia. This international initiative is based on information from more than 30 trials collectively including nearly 200,000 patients from the UK, Europe, US, China, Japan and Australasia. The collaboration brings together not only the data from the largest BP trials but also the expertise and experience of the principal investigators of these trials, who are leaders in their respective fields. To date, the Collaboration has provided important information about the effects of newer compared with older classes of BP-lowering drugs and about their effects on stroke, coronary heart disease in patients of different age, sex, and disease status. These findings have informed major international BP guidelines as well as clinical practice. A major challenge to this research is to ensure continually that the research is translated into practice. Huge gaps between evidence and practice exist and large proportions of the global population at risk of blood pressure-related disease continue to remain untreated. Part of the problem is that doctors persist in using outdated models of treatment based on managing individual risk factors rather than consideration of the patient’s ‘absolute risk’ of experiencing a major cardiovascular event.
As new drug classes and new indications for treatment evolve, the work of the BPLTTC will continue to be a valuable source of reliable information about the effects of these important drugs.

Sub-Saharan Africa (SSA) contains a diversity of ethnic groups, cultures and countries (54 in all) of vastly different socio-economic status. Data from many parts of sub-Saharan Africa are poorly explored because of financial constraints. South Africa is one of the few countries where data are reasonably accurate. Available data focusing on black groups indicate that hypertension seems more common with increasing acculturation, with a group of truly rural dwellers still being relatively protected. However, it is not known what proportion of the African population lives in truly rural conditions, relatively immune to the advances of civilisation versus those succumbing to urbanisation either rapidly or gradually.
The prevalence of hypertension according to rural studies undertaken in the 1970s, 1980s and 1990s has generally been low: 4.1% in Ghana, 5.9% in Nigeria, 7% in Lesotho and 9.4% in the rural Zulu. The migration of people to urban settings led to an immense increase of BP due to change in diet of new arrivals in the cities and higher pulse rates due to psychosocial stress and hard work.
Salt intake and lack of potassium due to inadequate fruit and vegetable consumption are also main causes for hypertension here. Other factors are obesity, particularly observed in black females, whereas alcohol excess is a problem particularly in black males.
Because SSA is the world’s poorest continent, only low cost hypertension programmes can be afforded. The healthcare expenditure in many SSA countries is around US$10 per person annually in contrast to between US$2,000 and $5,000 in industrialised Western countries. The major health challenge is still HIV/AIDS which takes a large portion of healthcare resources. There is a lack of adequate financing for research, but a comprehensive CVD programme is absolutely necessary. Furthermore, there is inadequate financing for researchers who need to be trained in excellent research centres so that they can learn techniques in research methodology. It would be helpful if researchers from the developed world could provide expertise and engage in collaborative work. We need administrators and politicians in sub-Saharan Africa to be convinced of the value of research on risk factors in CVDs. Inadequate funds, inexperience and lack of infrastructure remain important barriers to hypertension diagnosis and therapy.
To sum it up: The effects of urbanisation which influence the prevalence of hypertension and CVDs in SSA are decreased physical activity, increased energy and fat consumption and increased psychosocial stress. This leads to obesity, dyslipidaemia, diabetes and an increase in blood pressure. The future approach to CVD prevention should be a population focus on societal change and not only individual focus on high risk factors. This should include primordial prevention, salt restriction and physical exercise.

Generally we can say that, with the political transformation in Poland over the last 15 years, the risk factors for CVDs have dramatically changed, some of them significantly decreased (e.g. smoking) and some increased (e.g. psychosocial factors). With regard to hypertension the consumption of too much salt is our main national problem. The recommended daily allowance is 7g but every Pole eats 10–15g, in poor families it is even 15–20g. The government began to take action last year with an information campaign on Polish TV and radio. Additionally, there are attempts to convince industry to replace sodium by potassium.
Education is the crucial factor in prevention and control of arterial hypertension. One step to increase public awareness was to make primary physicians measure BP during every patient visit.
The place of residence is also a major indicator for prevalence and a starting point for the control of hypertension. One can say that Poland, especially during the early and very rapid phase of political and economic transformation, has been separated into two sections: large cities and small cities (county boroughs) and villages. People in large cities have had much better access to the best medical treatment, so we have many more cases of severe heart failure in the countryside, for example. Consequently, the hospitalisation rate of the rural population has been much higher in the last 15 years.
However, we have made significant progress in recent years,
due to huge investments and the long term and complex health policy project – National Cardiovascular Diseases Prevention and Treatment Programme (POLKARD 2003-2008).  For example, Poland now has a tight nationwide network of interventional cardiology and cardiac surgery centres. Access to these procedures dramatically improved and large inequalities significantly decreased. For example, in 2002, 2,300 coronary angiographies were performed per million people, and almost 900 percutaneous coronary revascularisation interventions (PCI), the respective numbers in 2007 were 3,850 coronary angiographies and 2185 PCI.
I hope this improvement in access to best procedures, changes in population awareness, healthier diet and less smoking are the most important factors responsible for a 30% reduction in CVD premature mortality in our country. This year we want to check this hypothesis and calculate the importance of each factor using the IMPACT model elaborated and published in most prestigious medical journals by Prof Simon Capewell from the University of Liverpool.
One side effect of the transition to a market economy was that we lost our national industry and the drugs to treat arterial hypertension became more expensive. Furthermore, primary care was privatised which, in the beginning of this process, especially in small cities and villages, made access to basic medical care more difficult. However, over the last five years we have observed an opposite trend and social and medical awareness of arterial hypertension is increasing again. At the moment about 66% of the population who have arterial hypertension know about it.
Another important problem is the very poor control of people who already had a stroke or myocardial infarct. I am the coordinator of an international study for Poland, Ukraine and Russia. This shows that very few patients receive adequate post-myocardial infarction or post-stroke treatment. My most recent project is the 400 Cities Programme, a very large-scale educational and prevention project to fight CVDs. We focus on the smaller cities, where the epidemiological situation is worse than in large cities and, for example, offer special classes in primary schools or special training for the nurses, doctors and administrative staff responsible for healthcare in their cities.

01.09.2008

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