Want to avoid stroke? Watch your blood pressure

We all know that diet and lifestyle can have a profound effect on wellbeing, but which aspects matter most? Is smoking more dangerous than drinking? And how do both compare with being overweight or stressed? Questions that an international team of researchers have just answered in relation to one of the biggest threats to our health: strokes.

Whether caused by a brain haemorrhage or a blood clot, strokes vie with cancer and heart disease as the biggest killers — and disablers — in the western world. And it is not just the elderly who are at risk. Every year in the UK there are 10,000 strokes in people under 55.

The Interstroke study, published in the this edition of The Lancet, identifies the ten most important modifiable risk factors for stroke and ranks them in importance (see below). The factors themselves won’t raise too many eyebrows among Times readers (I hope), but their relative importance might.

Blood pressure is also the easiest risk factor on the list to miss

high blood pressure headlines with medical instruments

High blood pressure tops the list by some margin, having nearly double the impact of physical inactivity, which is second in the ranking, and nearly ten times that of stress, which sits close to the bottom of the list. To put it another way, if you want to take one sensible precaution against an early stroke it should be to keep an eye on your blood pressure.

Blood pressure is also the easiest risk factor on the list to miss. Contrary to pub lore it rarely gives you a red face or constant headaches. It tends to be silent and pernicious, and the longer it remains undiagnosed the greater the damage to the delicate lining of the blood vessels resulting in the changes responsible for most strokes.

High blood pressure can develop at any age but is most common in the over-forties, affecting at least one in five adults in the UK to some degree at some time. The only reliable way to pick it up is to monitor it regularly — at least every five years from the age of 35 and annually if it’s found to be borderline.

But what is normal? It depends where the reading is taken. In your GP surgery you are likely to be told you have high blood pressure if your readings are consistently above 140/90. Yet in the more relaxed environment of your home the upper limit of “normality” is thought to be lower at 130/80-85.

Simple blood pressure chart showing systolic (top) and diastolic (bottom) reading

Simple blood pressure chart showing systolic (top) and diastolic (bottom) reading

Once a series of higher than ideal readings has been recorded the next step is to do something about it. This is where many people go wrong. It is not all about taking a pill to correct the numbers, although that will be an essential part of therapy for many people. Rather your first step should be to look at the risk factors identified by Interstroke and mitigate as many as you can. This can lower your blood pressure and have myriad other benefits too.

The next question is how low should you go? Up until now doctors have generally been content to see their patients’ blood pressure readings drop just below the upper limit of normal, but there is evidence that lowering it further offers protection. Recent American research suggests that aiming for 120/80 could reduce cardiovascular complications such as stroke, heart attack and heart failure by nearly a third more than the current targets.

However, there is a downside to having too low a pressure. It can make you feel lightheaded, particularly on standing or getting out of a warm bed or bath, and that carries a risk of falls, particularly in the elderly. And the type and dose of the more aggressive medication needed to achieve these lower targets tends to have more side-effects, including kidney problems. It is a matter of balance.

Fortunately, lifestyle interventions — such as taking up exercise, losing weight, eating a Mediterranean, low-salt diet, etc — have few if any worrying side-effects. So start with self-help measures and use medication as an adjunct, not a substitute. Treat your whole body and not just the numbers.

MODIFIABLE RISK FACTORS FOR STROKE IN ORDER OF IMPACT

  • High blood pressure, physical inactivity, abnormal blood fats (not just high cholesterol), poor diet and obesity are the top five accounting for most strokes
  • Smoking and underlying heart issues (such as atrial fibrillation) sit in the middle of the ranking with alcohol, stress and diabetes at the bottom
  • For an overview of the UK guidance on measuring and diagnosing high blood pressure visit Nice for guidelines

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