(The Guardian) — It was on a routine visit to the doctor that my GP uttered the phrase every middle-aged man dreads: “Your blood pressure is a little raised.” In fact my BP was 150/95mm Hg, well above the current “risk” threshold that the National Institute for Clinical Excellence (Nice) deems acceptable.
My elevated reading came as a shock, not least because I had always assumed I was in a low-risk group for stroke and heart disease: I don’t smoke, I’m not overweight, I exercise regularly, and I eat plenty of green vegetables. Indeed, until my mid-40s my BP had always hovered around 120/80, which used to be considered perfect (about which more later). Now, all of a sudden at the age of 47, I was being diagnosed with stage one hypertension and being assessed for a course of blood pressure reducing medications (see box, below).
According to Professor Graham MacGregor, the chairman of the Blood Pressure Association and professor of cardiovascular medicine at Barts and the London School of Medicine, I’m one of the “lucky” ones. Hypertension affects a quarter of the British adult population and accounts for 60% of all strokes in the UK and half of all heart attacks, but because the condition is usually symptomless most people have no idea they are at risk until it is too late. “Hypertension is a silent killer,” says MacGregor. “You’re bloody lucky to have discovered it at an early age and been given the opportunity to do something about it.”
MacGregor is probably right but I do not feel lucky. Having always enjoyed rude health, I did not wish to be admitted to the “kingdom of the sick”. Nor did I relish the prospect of having to take two, three, or however many pills every day for the rest of my life. My dilemma was not helped by the fact that defining hypertension is far from straightforward. Fifteen years ago, a BP reading of 150/95 would not have been a cause of particular concern (the threshold then was 160/100). But in the UK the bar is now set at 140/90 while in the United States the American Medical Association recently introduced a new category of “pre-hypertensive” for patients whose BP ranges between 120/80 and 140/90.
Then there are claims and counterclaims about the role of salt in elevating blood pressure, and the suspicion that a new hypertension polypill, Sevikar HCT, now available on the NHS, could be prescribed to everyone over the age of 55 as a matter of course, making blood pressure treatment as common as the fluoridation of water.
Nor is the picture made any clearer by the recent identification of 16 new genes for blood pressure. When I first heard about the discovery in September, I assumed a genetic test could not be far off. Led by researchers at Barts and the London, the study involved a survey of 200,000 people of European descent and 75,000 people of non-European descent, and brings to 28 the total number of blood pressure gene pathways identified to date. However, while the Barts team found that 5% of the gene variants were common to all population groups, collectively the genes had a very modest effect on blood pressure, accounting for less than 1mm Hg of the reduction in systolic readings and 0.5mm Hg of the reduction in diastolic reading across populations (The first number refers to blood pressure when the heart is pumping; the second number refers to blood pressure between beats.)
Indeed, the lead authors of the study, Mark Caulfield and Patricia Munroe, now suspect there may be hundreds of genes responsible for the regulation of blood pressure, each one with very small effects, meaning that a useful genetic test lies some way in the future.
Like many people for whom diet and weight do not appear to be significant factors, I have long suspected my hypertension has both a genetic and an emotional component. My mother, who is 79, developed stage two hypertension, defined as 160/100mm Hg or higher, in her 60s, and scientists now estimate that 30% of the observed variations in blood pressure are the result of genetic predisposition. Furthermore, although my father’s blood pressure was always well within the normal range, he was prone to mood swings of the “blood-boiling” variety and, like his father before him and his father before him, died of a heart-related condition in his 70s. While it is difficult to say whether I have “inherited” a similar disposition, I am certainly prone to sudden, irrational rushes of anger. Moreover, in a recent study Peter Rothwell, professor of clinical neurology at the John Radcliffe hospital, Oxford, found that blood pressure varies far more widely than is commonly assumed and can swing wildly throughout the day and over the course of the working week. “It’s the peaks in blood pressure that are most closely correlated with stroke risk, not mean blood pressure,” says Rothwell. “The key to controlling blood pressure is consistency – ironing out those swings.”
Then there is the intriguing question of the extent to which blood pressure is conditioned by environmental stresses and one’s temperament. For instance, it has long been known that the kidneys play a key role both in the regulation of blood pressure and the “fight or flight” response, a relationship that suggests a deeper evolutionary connection between blood pressure and our various emotional and psychological states. As the phenomenon known as “white coat syndrome” attests, the mere fact of having one’s blood pressure taken by a medical professional is sufficient to send some people’s readings soaring, while meditation and acupuncture have been shown to lower BP, albeit temporarily. Moreover, it is well known that people who report higher levels of stress at home or work, or have suffered a recent “life” blow, such as the death of a spouse, are more likely to suffer stroke or heart attack (in one study of work-related stressors, for instance, approaching deadlines were associated with a sixfold increase in myocardial infarction). Frequent anger and hostility have also been shown to predict coronary events. Thus in one community study patients with normal blood pressure but high anger temperament scores (as characterised by frequent or long-lasting anger reactions with little or no provocation) were shown to have an odds ratio of 2:3 for fatal or non-fatal cardiac events. While expert opinion differs over the extent to which blood pressure may be a factor, Rothwell points out that it is well known that stress raises BP and that people who are exposed to stressful situations experience greater blood pressure volatility. “I know that when I have to chair an important meeting or give a series of lectures my systolic reading can be as high as 180. That’s almost certainly due to stress,” says Rothwell. But while the bond between blood and emotion is embedded in everyday language – we talk of people being “sanguine” or “hot-blooded” – the average GP tends to have little time for such insights.
When we are young our bodies can more easily accommodate sudden fluctuations in blood pressure, but as we get older our blood vessels become stiffer and less flexible.
This is particularly a problem in the west and in Asian societies such as Japan. The question is why? Many experts believe the answer is salt.
For instance, the Yanomami tribe of Brazil, who eat a diet low in salt and saturated fat and high in fruit, have the lowest mean blood pressure of any population on earth – 95/61. Nor does their blood pressure increase with age. By contrast, in the west, where people eat an average of 10-12 grams of salt per day, blood pressure rises with age by an average of 0.5mm Hg a year. That may not sound a lot, but over the average lifespan that is a difference of between 35 and 44mm Hg systolic. Moreover, the most recent meta-analysis of trials involving more than 6,000 people from around the world, found that a reduction in salt intake of just 2mm a day reduced the risk of cardiovascular events by 20%. According to Professor MacGregor, who also chairs Consensus Action on Salt and Health (Cash), in serious scientific circles the connection between salt and higher blood pressure is no longer disputed. Yet for all the scientific consensus, salt-denial stories continue to enjoy wide currency in the media.
“The salt industry is trying to create the belief that there’s a controversy out there, and if the experts can’t agree how on earth can the man in the street make an informed decision,” says MacGregor. “But the fact is we have seven or eight different types of evidence that all point to the role of salt and I know that if I cut your salt intake by half it reduces blood pressure.”
To the coalition government’s credit, Britain now leads the way in salt reduction, with more than 40 food manufacturers having agreed to reduce the salt content of supermarket foods by 40% by 2012, followed by a further 15% cut thereafter. At the same time, Nice has called for the acceleration of national salt reduction targets, with the aim of reducing the average British adult’s intake to 6g a day by 2015, and 3g by 2025.
For all the publicity about the dangers of hypertension, however, most people remain blissfully unaware they are at risk. One of the biggest surprises for me was the discovery that my diet was not nearly as good as I thought it was: indeed, on some days I was consuming as much as 10g of salt, nearly twice the recommended amount (this is a particular problem at Christmas: a turkey dinner adds up to around 15g).
In the weeks and months that followed my diagnosis, I cut out processed foods and bread (one slice of bread contains an average of 0.5g, so if you eat six slices a day, that’s half your daily allowance) and upped my consumption of fruit and vegetables.
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