Thursday, August 16, 2007

Hypertension: uncontrolled and conquering the world

Hypertension: uncontrolled and conquering the world

The Lancet 2007; 370:539


When did you last have your blood pressure measured? In their Seminar on essential hypertension, Franz Messerli and colleagues point out that the risk of becoming hypertensive during lifetime exceeds a staggering 90% for a person in a developed country. The increasingly common combination and interaction of obesity, diabetes, hyperlipidaemia, and high blood pressure, if left untreated for too long, leads to cardiovascular disease, stroke, renal failure, dementia, and ultimately death.

Worldwide, the estimated number of adults with hypertension was 972 million in 2000; 639 million live in developing countries. By 2025, the total number is expected to increase to 1·56 billion. Lifestyle factors, such as physical inactivity, a salt-rich diet with processed and fatty foods, and alcohol and tobacco use, are at the heart of this increased disease burden, which is spreading at an alarming rate from developed countries to emerging economies, such as India and China. And even countries in Africa are noticing a sharp increase in patients with hypertension, at least in urban settings. For example, in 2006, hypertension was the second most reported medical condition in greater Accra, Ghana, up from fifth in 2005.

Hypertension remains a problematic disorder, even in developed countries with functioning health-care systems, a large number of available effective treatments, and overwhelming research evidence in relevant populations, for several reasons. Screening for hypertension is not done systematically and the diagnosis is often made at a late stage when target-organ damage has already happened. The optimum time to start treatment remains under discussion. All guidelines still use the threshold model for recommendations, in which hypertension is diagnosed when the systolic blood pressure exceeds 139 mmHg or the diastolic blood pressure is higher than 89 mmHg. The Seminar authors and the new guidelines by the European Society of Cardiology (ESC) published this July acknowledge that this model is arbitrary and scientifically questionable. It has been shown, for example, that there is a continuous relationship with cardiovascular risk down to levels of 115–110 mmHg systolic, and 75–70 mmHg diastolic, blood pressure. This finding led to the notion of “prehypertension” in the USA, or “high-normal” blood pressure in Europe. People in this category are advised to modify their lifestyle, an approach with very limited success, and they may be treated if they are in a high-risk category.

Risk assessment, important for treatment decisions, is another problem not yet solved satisfactorily. Currently, risk is usually expressed as the absolute risk of having a cardiovascular event within 10 years. The ESC guidelines recognise that this approach gives too much weight to age and suggest that it might be more appropriate in young people to estimate the relative risk in comparison with their peers.

Hypertension is now diagnosed even in adolescents and children and if ignored could lead to a partly irreversible high-risk condition years later. How best to treat in this age group, however, is unknown. Last week, Novartis was granted a 6-month marketing exclusivity extension for valsartan by the US Food and Drug Administration under the Pediatric Exclusivity Rule, based on studies done in children with high blood pressure. The motive behind these studies, however, has much more to do with capturing the lucrative adult market for as long as possible than with finding a solution for children.

At the other end of the age spectrum, it was until now unclear whether people older than 80 years benefit from antihypertensive treatment in terms of reduced all-cause mortality. Last week, researchers from Imperial College, London, UK, announced the early stopping of a large trial in people over 80 years because of a highly significant reduction in stroke and all-cause mortality in the group treated with perindopril and indapimide.

The biggest problem, arguably, remains compliance. Despite very effective and cost-effective treatments, target blood pressure levels are rarely reached, even in countries where cost of medication is not an issue for patients. Many people still believe that hypertension is a disease that can be cured, and stop or reduce medication when blood pressure levels fall. Physicians need to convey the message that hypertension is the first, and easily measurable, irreversible sign that many organs in the body are under attack. Perhaps this message will also make people think more carefully about the consequences of an unhealthy lifestyle and help to give preventive measures a real chance of success.

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