Is your blood pressure normal? There's a one-in-six chance that you have hypertension (high blood pressure), and you don't know it. With this finding from a University of Hong Kong study last year - and in line with the theme of hypertension for Sunday's World Health Day - the Health Department is launching a city-wide publicity and public education campaign tomorrow.
Nearly 50 organisations, including medical associations and district councils, have pledged their support of the campaign to raise awareness of hypertension and encourage healthy living. Some are organising community blood pressure checking activities.
The large-scale cohort study by HKU's School of Public Health revealed that among those with hypertension documented in the study (about 32 per cent of adults aged 20 and above), only about half of them (46 per cent) were ever diagnosed as hypertensive.
Even so, Dr Wayne Lam, an in-house physician at Hong Kong Adventist Hospital, says hypertension cases are typically diagnosed in a doctor's office only incidentally because it is usually asymptomatic.
The HKU study also found that the management of hypertension is suboptimal. Among those diagnosed, 70 per cent were prescribed blood pressure lowering medication, but only 42 per cent of this treated group attained good control of blood pressure.
The study confirmed the "rule of halves" in hypertension: roughly half of all hypertensive cases are diagnosed, half of those diagnosed are treated, and half of those treated are well-controlled.
Equally worrying is the fact that hypertension patients in Hong Kong are getting younger. A recent fitness survey by the Leisure and Cultural Services Department (LCSD) identified 4.1 per cent of primary school students as being at risk of hypertension. For those aged 13-19, the figure was 7.5 per cent for boys and 1.2 per cent for girls.
"Although the numbers are low," say the researchers, "caution should be raised, as healthy children should not have such a chronic disease."
Dr Tony Wong of The London Medical Clinic adds: "We would expect the number of younger people with high blood pressure to go up along with their rising obesity rates."
A high-sodium diet raises blood pressure, which is a contributor to the development of cardiovascular disease. Eating too much salt contributed to 2.3 million deaths globally from heart attacks, strokes and other heart-related diseases in 2010, according to a new American Heart Association report.
Being obese - that is, having a body mass index of 30 or more - also increases the risk of developing the disease, says Dr Boron Cheng, specialist in cardiology at Matilda International Hospital.
If you have a family history of hypertension, especially if a first-degree relative suffers from it, your risk is increased because genetics is believed to play a role.
Age is another factor. As we get older, our blood vessels tend to lose their elasticity, and this can affect blood pressure. The LCSD survey found a significant increase in hypertension risk from young to old adulthood. Among adults aged 20 to 39, 16.4 per cent of men and 6.3 per cent of women suffered hypertension risk. This increased to 40 per cent and 35.1 per cent among men and women aged 60 to 69.
Other people at high risk, says Wong, include those with chronic kidney disease and mothers who developed pre-eclampsia during pregnancy - a condition characterised by high blood pressure, significant amounts of protein in the urine, and swelling of the hands, feet and face. Your lifestyle also may determine whether you develop high blood pressure later in life. Lam points out that having two alcoholic drinks a day makes you up to twice as likely to develop hypertension than a non-drinker. He adds that smoking 15 cigarettes or more a day is associated with a transient rise in blood pressure, with the effect more pronounced in the first cigarette of the day.
Chronic stress, too, can cause your blood pressure to spike, one theory being that stress hormones produced by the body can damage blood vessels and predispose you to hypertension.
There are four main classes of medication used to treat hypertension, but studies have found that most people will eventually need more than a single drug to control their blood pressure. As such, combinations of agents have been developed with two or even three drugs in one pill. This makes it more convenient for the patient and allows the drugs to work synergistically.
Much is also being done in the area of genetic research. To date, 28 gene regions associated with high blood pressure have been discovered. This may pave the way to developing specific gene-targeted therapy in the future, says Wong, but more work still needs to be done.
New treatments in the form of implantable blood pressure devices are being tested in the US and may prove useful for patients who don't respond well to standard medications.
"The pocket-sized Rheos machine is effectively a pacemaker for blood pressure," says Wong. "When it detects high blood pressure it sends electrical impulses to the carotid artery in the neck, stimulating the body's natural systems to reduce blood pressure."
Another new procedure involves the introduction of a wire into an artery in the groin that burns off a group of nerves associated with high blood pressure. Results have proved promising for the group of patients who have tried it.
High blood pressure can be controlled with modifications in diet and lifestyle. Minimising your salt intake will help greatly.
Lam says reducing your daily salt intake from 4 grams to 2.3 grams can reduce blood pressure by 5/3mm of mercury in hypertensive people.
Lose weight if you are overweight or obese, quit smoking, and limit your intake of saturated fat and sugary snacks. As vitamin D deficiency has been linked with high blood pressure, a daily supplement might be useful.
Exercise helps, too. Lam points out that regular cardiovascular exercise can reduce your blood pressure by as much as 5mm to 15mm of mercury, although this drop is associated more with the intensity of the exercise rather than frequency.