Are you at risk for hypertension?

 | January 1, 2007

Are you at risk for hypertension?

Essential hypertension has no known cause. As a result, identifying clear risk factors is difficult. Researchers have discovered a few patterns, however. Some factors you have no control over — for example, you can't alter your genes. But others, like smoking and heavy drinking, are habits you can change.

Back to top

Risk factors you can't change

Even though you can't control these risks, that doesn't mean you can forget about them. Awareness of your risk factors can help you put your overall cardiovascular risk profile into perspective and may provide you with extra incentive to adopt healthier habits.

Back to top

Race

Hypertension often develops earlier and with more ferocity in African Americans than in other races. African Americans are nearly twice as likely to suffer a fatal stroke, 1½ times more likely to die from heart disease, and four times more likely to suffer kidney failure than are whites. For black men, the picture is particularly disturbing — they face a death rate from disorders related to high blood pressure that's more than three times that of the death rate in white men.

The high incidence of hypertension among African Americans may have a genetic explanation. Some researchers suspect that people who lived in equatorial Africa developed a genetic predisposition to being salt sensitive, which means their bodies retain more sodium. This condition increases blood volume, which, in turn, raises blood pressure. Salt sensitivity can be beneficial in a hot, dry climate because it allows the body to conserve water. Generations later, however, the American descendants of these individuals remain disproportionately salt sensitive (see Figure 2).

On a positive note, the 1997 Dietary Approaches to Stop Hypertension (DASH) study showed that a low-fat diet rich in fruits, vegetables, and fiber was particularly beneficial to African Americans, especially when it was combined with additional limits on salt consumption (see "How the DASH diet helps").

Back to top

Family history

Hypertension, like many disorders, runs in families. In addition, a family history of heart attack, stroke, diabetes, kidney disease, or high cholesterol increases your risk of developing high blood pressure.

This doesn't necessarily mean, however, that genetics always plays a role. Some of the similarities observed in families may be the result of environmental influences. Children's eating patterns, coping skills, and propensity toward healthy and unhealthy habits are shaped by their parents' behavior and the social climate in which they're raised.

Research indicates that about 25% of cases of essential hypertension in families and up to 65% of cases of essential hypertension in twins may have a genetic basis. In addition, at least 10 genes have been found to influence blood pressure. So far, however, only a few studies have identified a link between particular genes and hypertension. For instance, a rare form of hypertension called Liddle's syndrome, which develops in childhood and often leads to an early death from cardiovascular disease, results from a defective gene that causes the kidneys to retain too much sodium and water.

Back to top

Age

Although aging doesn't invariably lead to hypertension, high blood pressure becomes more common in later years. Diastolic pressure increases an average of 10 mm Hg up to age 55 in men and age 60 in women, and then begins to decline. Between ages 30 and 65, systolic pressure increases an average of 20 mm Hg, and it continues to climb after 70. This age-associated increase largely explains isolated systolic hypertension.

Back to top

Sex

Up to about age 55, women have a lower incidence of hypertension and other cardiovascular diseases than men do. But women's blood pressures, especially the systolic readings, rise more sharply with age. Indeed, after age 55, women are at greater risk for high blood pressure. This pattern may be partly explained by hormonal differences between the sexes. Estrogen tends to protect women against cardiovascular diseases, including hypertension, but as the production of estrogen drops with menopause, women lose its beneficial effects, and their blood pressures climb.

Back to top

Controllable risk factors

Your health habits are key factors in determining your cardiovascular risk. In fact, you may be able to bring your blood pressure readings into a safe range simply by making changes in your lifestyle, such as quitting smoking and losing weight.

Back to top

Smoking

Doctors have long known that smoking promotes heart disease, but for a long time smoking didn't appear to have a direct connection to hypertension. Observations have revealed a crucial link that earlier studies missed because blood pressure is generally measured in doctors' offices and clinics, where smoking is prohibited.

When researchers tested blood pressure while people smoked, they discovered that within five minutes of lighting up, the subjects' systolic pressures rose dramatically — more than 20 mm Hg, on average — before gradually declining to their original levels over the next 30 minutes. This means the typical smoker's blood pressure soars many times throughout the day. Like people with labile hypertension (in which blood pressure may jump frequently in response to daily stresses), smokers may suffer "part-time" hypertension. For example, smokers with a prehypertensive reading of less than 140/90 mm Hg may actually have stage 1 hypertension every time they puff a cigarette.

This increase occurs because nicotine, whether smoked or chewed, constricts small blood vessels, forcing the heart to work harder to circulate blood. As a result, the heart speeds up and blood pressure rises. Nicotine also interferes with some antihypertensive drugs, most notably beta blockers. The chemicals in tobacco smoke raise heart disease risk in other ways, too. They can reduce the body's oxygen supply, lower levels of HDL ("good") cholesterol, and make blood platelets more likely to stick together and form clots that can trigger a heart attack.

Back to top

Excess salt

Doctors first noticed a link between hypertension and sodium chloride — the most common form of dietary salt — in the early 1900s, when they found restricting salt in patients with kidney failure and severe hypertension brought their blood pressures down and improved kidney function. When a massive effort began in the 1960s to educate the public about reducing the risk of heart disease, one recommendation was that all Americans decrease salt consumption to prevent hypertension.

Federal guidelines advise people to limit sodium intake to 2,300 milligrams (mg) per day — about the amount in 1 teaspoon of table salt. Yet Americans typically consume 1–3 teaspoons or as much as 7,200 mg a day (see Figure 3). This fact, coupled with the high prevalence of hypertension in the United States, led researchers to assume that salt overload was the culprit.

As it turns out, this may or may not be true. Nearly 50% of people who have hypertension are salt sensitive, meaning eating too much sodium clearly elevates their blood pressure and puts them at risk for complications. In addition, people with diabetes, the obese, and older people seem more sensitive to the effects of salt than the general population. However, the question of whether high salt consumption also puts generally healthy people at risk for hypertension is the source of considerable debate (see "Consume less salt"). Regardless of whether high salt intake increases blood pressure, it does interfere with the blood pressure–lowering effects of antihypertensive medications.

Back to top

Obesity

Excess weight and hypertension often go hand in hand because carrying even a few extra pounds forces your heart to work harder. People who are overweight or obese are also more likely to develop diabetes, heart disease, arthritis, gallstones, sleep apnea, gout, and some cancers.

High blood pressure is about six times more common in people who are obese than in those who are lean. Twenty-two pounds more weight boosts systolic blood pressure by 3 mm Hg and diastolic blood pressure by 2.3 mm Hg. These increases cause a 12% greater risk of heart disease and a 24% greater risk of stroke, according to a 2006 statement from the American Heart Association.

What's a healthy weight for you? Let the body mass index (BMI) guide you (see Table 2). A BMI of 25 to 29 indicates that an individual is overweight, while a BMI of 30 or above designates obesity.

Another thing to keep in mind is that it's not weight alone that matters, but also where you carry your extra weight. People with excess fat in the abdominal area (see Figure 4) are not only at greater risk for hypertension, but also for high cholesterol and diabetes. So if your BMI is 25 or more, and especially if you have accumulated abdominal fat, the unfortunate reality is that you need to lose weight.

Back to top

Sedentary lifestyle

Compared with the physically active, sedentary people are significantly more likely to develop hypertension and suffer heart attacks. Like any muscle, your heart gets stronger with exercise. A stronger heart pumps more blood more efficiently, with less force, through your body. Other cardiovascular benefits of exercise include losing excess weight, increasing levels of "good" HDL cholesterol, and making stroke-causing clots less likely.

Back to top

Heavy drinking

Excessive drinking — having three or more drinks per day — is a factor in about 7% of hypertension cases. It can also interfere with antihypertensive medications, increase your risk of stroke, and lead to heart failure.

While moderate alcohol consumption (no more than one drink per day for women and two drinks a day for men) significantly lowers your risk of cardiovascular disease and has little effect on your blood pressure, heavier drinking has the opposite effect. How alcohol raises blood pressure is unknown, but it appears that once you go past two drinks per day, the more you drink, the higher your blood pressure. This effect becomes more pronounced as you age and occurs regardless of what type of alcohol you drink.

Back to top

Review Date: 2007-01-01

Harvard Medical School does not endorse products or services.