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Experts call for focus on systolic in patients over 50

Research recommends that only systolic blood pressure should be used to measure and diagnose hypertension in patients over 50. Nerys Hairon reports

Measuring and diagnosis of hypertension should be carried out using systolic blood pressure only in patients aged over 50, research recommends (Williams et al, 2008). Current practice involves using both systolic and diastolic pressures. This research, published online as a viewpoint article by The Lancet, argues that, due to ageing populations, systolic hypertension is becoming much more common and important due to its high prevalence in patients over 50, compared with diastolic hypertension.

The authors propose a simplified view of hypertension for patients over 50, whereby the thresholds for diagnosis and treatment are expressed in one dimension – systolic BP. They suggest that using only one number will help to communicate an important public-health message to patients, and to simplify treatment targets and thresholds for healthcare professionals.

Background

Hypertension is common; 40% of adults in England have the condition (NHS Direct, 2008), with around 16 million people in the UK affected overall. For reasons that are not entirely understood, people of African-Caribbean and South Asian (India, Pakistan and Bangladesh) origins are more likely to develop hypertension than other ethnic groups. In 95% of cases, there is no single identifiable reason for an increase in BP. However, all available evidence demonstrates that lifestyle plays a significant role in regulating BP. Risk factors for hypertension include:

  • Age;

  • Excessive alcohol consumption;

  • Poor diet;

  • Lack of physical activity;

  • Obesity.

Context

Hypertension is becoming an increasingly important condition to measure, diagnose and manage. An editorial in The Lancet last year warned of a massive increase worldwide in the number of adults with hypertension over the next two decades (The Lancet, 2007).

In addition, the Department of Health recently announced plans to introduce vascular screening for all people aged 40–74 in 2009–2010 (Vascular Programme, 2008; Hairon, 2008). This programme has identified hypertension as a modifiable risk factor in preventing or delaying the onset of vascular disease. NICE (2006) stressed that hypertension is a major but modifiable contributory factor in cardiovascular diseases such as stroke and coronary heart disease. It is important to assess risk in people before cardiovascular disease develops, and monitoring for persistently raised BP is one aspect of cardiovascular risk assessment.

While the details on implementing the DH’s vascular screening programme are still being worked out, practice nurses and other community practitioners will play a vital role in carrying out vascular screening (Hairon, 2008). These new recommendations on targeting systolic BP in people over 50 apply to a large proportion of those in the age group highlighted for screening in the DH programme.

The effect of age

Williams et al (2008) point out that BP profiles change with increasing age. Systolic pressure rises with age; however, diastolic pressure increases until around the age of 50, and then falls after this point. This is at a time when the risk of cardiovascular disease begins to increase. Consequently, there is an increased prevalence of high systolic BP in people over 50, while high diastolic pressure almost totally disappears in this group. The authors assert that since more than 75% of people with hypertension are aged over 50, the burden of disease is mainly due to systolic BP.

The emergence of systolic hypertension as the major risk factor relates to two major changes – people are living longer and people with hypertension are generally being diagnosed and treated earlier, the authors say. Consequently, severe diastolic hypertension is becoming less of a problem, while the under-treatment of raised systolic BP is being exposed.

Treating systolic hypertension
As diastolic BP falls from the age of 50 and older populations increase, Williams et al (2008) point out that the population burden of cardiovascular disease attributable to BP will be almost entirely related to systolic pressure. This assertion is based on the theory that the risk of cardiovascular disease is related to high systolic BP rather than low diastolic pressure over the age of 50. This has been tested in trials of older patients with mainly isolated systolic hypertension. Treating this condition lowers both systolic and diastolic pressures. Trials to lower BP in patients with isolated systolic hypertension have demonstrated the safety and cardiovascular benefits of lowering systolic BP. In addition, they have not shown that a resulting fall in diastolic pressure would cause harm or offset the benefit of a decrease in systolic BP.

The authors also argue that targeting diastolic pressure leaves most patients with uncontrolled systolic BP. However, if treatment was focused on systolic pressure, this would mean diastolic BP would hardly ever not be controlled.

Consequently, the authors propose that, in patients over 50, only systolic BP needs to be measured, for four main reasons (see box).

Reasons to focus on systolic BP in patients over 50

  • Systolic blood pressure is more easily and accurately measured than diastolic pressure, and is a better predictor of risk.

  • Using just one number would make communication with patients easier, since using two different numbers has left many confused about the relative importance of systolic versus diastolic BP.

  • Many doctors have also been confused by conflicting messages about diastolic and systolic BP, and many still use diastolic pressure in order to guide treatment decisions.

  • Focusing a public-health campaign on a single number for patients over 50 could dramatically improve treatment and control of systolic BP and further reduce associated cardiovascular morbidity and mortality.

Systolic BP targets

The authors discuss the issue of optimum targets for systolic BP treatment. They say that the risk of cardiovascular disease rises continuously as systolic pressure increases from 115mmHg. Most international and national guidelines advocate a target of below 140mmHg, with a target of below 130mmHg for patients with diabetes and those with raised cardiovascular risk for other reasons.

However, the authors state there is a lack of evidence from prospective randomised clinical trials to define the best target for systolic BP treatment, and such trials are much needed.

Patients under 50

Williams et al (2008) acknowledge that for patients under 50, the scenario is different. In people under 40, as many as 40% of patients with high BP have isolated diastolic hypertension, and in those aged 40–50, this figure is around one-third. Therefore, in patients under 50, a continued emphasis on both diastolic and systolic pressures is appropriate. However, the authors warn that the focus in this much smaller group of patients should not dilute the key message regarding the importance of systolic BP for the majority of patients with hypertension.

Conclusion

The authors emphasise that BP should be seen in the context of a patient’s overall cardiovascular risk, and point out that many patients at high risk will need more than just ways of lowering BP to optimise risk reduction. They want to shift the focus from diastolic to systolic pressure to both define the risk associated with hypertension and the treatment target.

Williams et al (2008) believe that systolic BP should become ‘the sole defining feature of hypertension and key treatment target’ for people over 50. Even for those under 50, while diastolic BP should always be controlled, systolic pressure should be the main target. They argue that the current emphasis on diastolic pressure often leaves those most at risk with uncontrolled systolic BP. A renewed focus on systolic pressure would aid the prevention of BP-related cardiovascular disease.

Since nurses are vital in measuring and monitoring BP, this research serves to emphasise the importance of systolic BP in patients over 50.

References

Hairon, N. (2008) Vascular screening programme moves focus to early prevention. Nursing Times; 104: 15, 19–20.

NHS Direct (2008) Blood Pressure (High).www.nhsdirect.nhs.uk

NICE (2006) Hypertension: Management of Hypertension in Adults in Primary Care. London: NICE. www.nice.org.uk

The Lancet (2007) Hypertension: uncontrolled and conquering the world. The Lancet; 370: 9587, 539.

Vascular Programme (2008) Putting Prevention First. Vascular Checks: Risk Assessment and Management. www.dh.gov.uk

Williams, B. et al (2008) Systolic pressure is all that matters. The Lancet, published online 17 June 2008. www.thelancet.com

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