In this article number 3
- Looking at the demographics of high blood pressure
- Discovering what you can and can’t do to bring down high blood pressure
Many factors play a role in the development of high blood pressure. Although you can’t control some (like your family history, ethnic background, age, and gender), you can control others such as diet, exercise, stress, your smoking and drinking habits, and a tendency to park as close to the exercise facility as possible.
Each factor may be present to a greater or lesser extent in a particular area of the world, so the prevalence of high blood pressure is low in some places and extremely high with severe consequences in other places (see Part II).
In this article, we discuss both the uncontrollable and the controllable factors related to the development of high blood pressure. If you haven’t been diagnosed with high blood pressure, be sure to read up on the controllable factors that can help lessen your chances of developing it. If you have been diagnosed with high blood pressure, be sure to read Part III, where we discuss the same controllable factors in relation to treating high blood pressure.
Note: One factor that causes your blood pressure to rise is forgetting your spouse’s birthday. Running over your son’s bike when you back into the garage is another. Fortunately for you, the rise from this kind of event is only temporary!
The various factors leading to high blood pressure that I mention in this article are far from inclusive. I stress the most important ones, but scientists are continually discovering other factors that cause high blood pressure.
Clarifying What You Can’t Control
This section describes the factors in your life that you can’t control. You can’t alter your family history, ethnic background, gender, and age. Note: These uncontrollable factors aren’t quite the same as when you let a shirt hang in your closet for a while and it shrinks two sizes!
Although you can’t control some factors, you still need to know how they contribute to high blood pressure, and you need to be cautious. Allow your-self to become obese, and you may have high blood pressure even though you’re in a low-risk group.
Looking at the global picture
The prevalence of high blood pressure throughout the world breaks down into four major categories as follows:
- Zero: A few isolated groups such as those in the Amazon have zero high blood pressure.
- Low: The incidence of high blood pressure is low (below 15 percent) in the rural populations of Latin and South America, China, and Africa.
- Normal: Most often, high blood pressure prevails in 15 to 30 percent of a given population including most industrialized areas — Japan, Europe, and the Caucasian population of the United States.
- High: A high percentage (30 to 40 percent) exists in the Russian Federation, Finland, Poland, and among African Americans.
Wherever high blood pressure occurs, heart, brain, and kidney complications (see Part II) are similarly high. The burden of disease due to high blood pressure is enormous in countries like the Russian Federation, but no more than among African Americans. (See the “African Americans” section later in this chapter.) Stroke (brain attack), usually related to high blood pressure, is the second leading cause of death in Japan, and researchers continue to emphasize the control of blood pressure to prevent strokes (Stroke, August 2001).
Several studies conducted throughout the world on high blood pressure show that a high percentage of high blood pressure often coexists with poor awareness and insufficient treatment. For example:
- A study in the Archives of Brazilian Cardiology (July 2001) shows that the percentages of high blood pressure in Brazil are similar to the United States’ numbers, but because of a combination of poor awareness and poor treatment, only a fraction of that Brazilian population can control it.
- Several European populations are aware of their high blood pressure but are unable to control it. For example:
- In Spain, a blood pressure of 160/95 mm Hg (rather than the 140/90 mm Hg recommended by JNC 7; see article 2) is the cutoff point to begin treatment.
- In France, both awareness and treatment are inadequate.
- Although many South Koreans have high blood pressure and receive treatment, few South Koreans are able to control their high blood pressure according to a study in the Journal of Hypertension (September 2001).
Before you pack your bags and fly off to the Amazon in hopes of living a long, illness-free retirement in a tropical paradise, please consider this possibility: If a high percentage of high blood pressure often coexists with poor awareness and insufficient treatment, then perhaps low percentages can coexist with acute awareness and sufficient treatment — without a trip to the Amazons! Read on.
Accounting for the contribution of your genes
High blood pressure tends to run in families, so a family history of the condition can predict its development in relatives who have normal blood pressure. For example, when comparing biological children with adopted children, the same or similar blood pressure measurements were shared between biological parents and their children to a greater degree than between adopted children and their parents. Bottom line? If you have two or more relatives who developed high blood pressure before the age of 55, you’re at much higher risk of developing it yourself. (Next time around, try to pick your parents a little more carefully!)
Researchers still don’t know exactly how and which genes are responsible for high blood pressure, but they do believe many genes contribute to the condition. In other words, having one particular gene doesn’t predict high blood pressure — and even if they find the right ones, today’s scientists can’t alter genes.
Heredity also affects body weight. People who are closely related tend to have similar degrees of obesity, which plays a large role in the development of high blood pressure. (See the “Controlling your weight” section later in this article for more details about the effect of excess pounds.)
The Stroke Belt
The Stroke Belt includes most of the southeastern United States with the exception of Florida. The greater prevalence of high blood pressure in this area means that large numbers of strokes (brain attacks) occur there. In fact, deaths due to brain attacks in that area are more than 10 percent above the national average. But brain attacks aren’t the only consequence of high blood pressure. Other complications such as kidney failure and heart failure occur far more often in the Southeast than throughout the rest of the country. (For more on brain attacks, kidney failure, and heart failure, see Part II.) In addition, the overall death rate is higher in the southeastern states as compared to the rest of the country. Caucasian men in the Southeast have a some-what higher prevalence of high blood pressure compared to the rest of the country. But low birth weight and high blood pressure are more frequent among African Americans in the Southeast, the area of the country where most African Americans live. However, the reasons that African Americans in the southeastern United States have such high rates of high blood pressure and death due to its complications are no different from the reasons for high blood pressure in general:
- High salt intake is common in the Southeast, especially among African Americans.
- Low potassium intake from fruits and vegetables is usual.
- Obesity occurs in a much greater percentage of the population.
- Physical inactivity is the rule in the Southeast. Half of the population doesn’t get enough exercise.
The insulin resistance syndrome may be a particularly important example of the role that inheritance plays in high blood pressure. People with this condition have
- Increased insulin (the hormone that controls blood sugar) and at the same time reduced sensitivity to their insulin
- A typical pattern of blood fats consisting of high triglycerides (the type of fat on meat — greater than 200 mg/dL) and low HDL cholesterol (the blood fat particle that protects against heart attacks — less than 30 mg/dL)
In addition, people who suffer from insulin resistance syndrome
- Are usually but not always obese
- Tend to have a much higher incidence of fatal heart attacks
- May make up 20 percent of all high blood pressure cases
- Tend to carry their fat around the waistline
Estimating the effects of ethnicity
According to the United States Centers for Disease Control and Prevention, the prevalence of high blood pressure was reduced among men and women in every ethnic group between 1960 and 1990, but then the prevalence increased between 1990 and 2002 (the last year for which data is available). Some representative differences are shown in Table 3-1.
(to follow soon with updated data)
Table 3-1 Percentage of United States Population Age 20 and Older with High Blood Pressure* Group 1960 1970 1980 1990 2002 Both sexes 36.9 38.3 39.0 23.1 33.6 Male 40.0 42.4 44.0 25.3 30.6 Female 33.7 34.4 34.0 20.8 31.0 Caucasian Male 39.3 41.7 43.5 24.3 32.5 Caucasian Female 31.7 32.4 32.3 19.3 31.9 African American Male 48.1 51.8 48.7 34.9 42.6 African American Female 50.8 50.3 47.5 33.8 46.6 Hispanic Male 25.0 25.2 26.3 Hispanic Female 21.8 22.0 23.4 *Percentages provided by the U.S. Centers for Disease Control and Prevention.
The table shows the great strides that have been made to reduce the prevalence of high blood pressure in this 42-year period. But the table indicates that nearly a third of the age-20-and-older population suffers from high blood pressure and two out of five African Americans have high blood pressure. When coupled with appropriate medical attention and lifestyle changes (which we describe later in this article), awareness of these factors can lower the number of high blood pressure cases in the United States.
African Americans — the population most at risk in the United States for developing high blood pressure and its consequences — develop high blood pressure twice as often as Caucasians. In addition, African Americans:
- Have a high rate of end-stage renal disease (kidney failure), which may be due in part to their increased level of high blood pressure
- May have an inherited kidney defect that limits their ability to handle salt
- Have a lower response to nitric oxide (a necessary compound in the blood vessels) than Caucasians (For more on nitric oxide, see below: “Nitric oxide to the rescue” section.)
In addition, the stresses associated with low socioeconomic status are frequently blamed for at least some of the high blood pressure among African Americans. Dietary treatment, however, has been particularly successful among African Americans with high blood pressure. One of the best approaches has been the Dietary Approach to Stop Hypertension (DASH diet — see article 9), which consists of increased amounts of fruits, vegetables, grains, low-fat dairy products, and low-fat protein.
The prevalence of high blood pressure among Hispanics is generally similar to Caucasians. Although the incidence of high blood pressure is greater among African Americans, Hispanic adults tend not to take medication for their high blood pressure as often as Caucasians or African Americans.
About 30 percent of adult Caucasians in the United States have high blood pressure. Caucasians, as a group, seem to be more aware of their high blood pressure and get treatment more often than African Americans or Hispanics. However, Caucasians’ treatment is satisfactory only about 20 percent of the time, so they also have much room for improvement; in this case, the problem is often due to a lack of patient compliance with the medication.
Nitric oxide to the rescue
The cells that line the inside of the blood vessels produce nitric oxide, a potent compound that widens blood vessels and reduces blood pressure. A number of risk factors for cardiovascular disease cause damage to these cells and inhibit their ability to produce nitric oxide. These risk factors include:
- High blood pressure
- High cholesterol
- Insulin resistance
- Postmenopausal lack of estrogen
- Tobacco smoking or chewing
When these risk factors are present, they also make the individual more susceptible to the blood-pressure-raising effect of stress. Reversing these risk factors eliminates their damaging effects and helps restore nitric oxide production. Part III explains ways to attack any of these risk factors.
Identifying the culprits: Salt and fat
By comparing people of the same race in different areas of the world, a 1999 study in Scientific American sought an explanation for the high rate of high blood pressure among African Americans. The authors, dissatisfied with a genetic explanation, found great differences between Africans living in Nigeria, Jamaica, and the United States:
Nigerians are generally lean, do physically demanding work, and eat a traditional Nigerian diet of rice, vegetables, and fruits. Blood pressure doesn’t rise as they get older, and high blood pressure is rare.
The Jamaican diet is a mixture of home- grown and commercial foods. They tend to live six years longer than African Americans because the incidence of cancer and heart disease is lower.
In Maywood, Illinois, an African American community just outside of Chicago, the migrants from the southeastern United States have a high-salt, high-fat diet.
Although all the groups had a common genetic background, the percentage of the population with high blood pressure was 7 percent for the Nigerians, 26 percent for the Jamaicans, and 33 percent for the African Americans. The Americans also had greater body weight, greater salt intake, and less potassium intake than Nigerians.
The authors concluded that no racial explanation exists. High blood pressure in African Americans isn’t genetic because African Americans with high blood pressure and those with normal blood pressure share the same genes. The study emphasizes that explanations for the various results should be sought in the environment and not in the genes. The Nigerians ate less salt, consumed more potassium, and were much more physically active.
Focusing on gender
Boys are much more likely than girls to have higher systolic blood pressure (the amount of pressure in your arteries as the heart pumps; see article 2 for more details). In a study in the December 2006 Circulation, starting at age 12 and every two years thereafter, high blood pressure increased 19 percent in boys but was stable for girls in Canada. The key factors were a sedentary lifestyle and lack of exercise in both boys and girls. We say a lot more about high blood pressure and children in article 15.
In young adults (ages 18 to 35), high blood pressure is more prevalent in men than women. But after women reach the age of 50 (when most women lose their estrogen through menopause or removal of their ovaries), women have a higher prevalence of high blood pressure than men.
However, more often than men, women tend to be aware of their high blood pressure, get treatment for it, and control it. The explanation for this difference may be that women see doctors more frequently due to pregnancies, pelvic exams, and breast exams — all opportunities for the doctor to note high blood pressure.
Similar to men, women reduce their risk of brain attack when treated for high blood pressure, so treatment should be given to women just as often as it’s given to men.
In the following sections, we describe the effects of oral contraceptives and menopause on women’s blood pressure.
Taking oral contraceptives
Previously, oral contraceptives contained more estrogen and progesterone than they do today, and their use was associated with more heart disease, heart attacks, brain attacks, and a higher death rate. Current preparations contain less hormone and do not cause those complications, especially in comparison to other methods of contraception. However, oral contraceptives can cause a slight increase in blood clots and breast cancer, so a woman who has had blood clots in the past should not take oral contraceptives.
Oral contraceptives are associated with some rise in blood pressure, which subsides when the contraceptive is discontinued. However, once in a while, oral contraceptives can bring on more severe high blood pressure. If a patient has a family history of high blood pressure or kidney disease, the physician needs to be cautious about giving her oral contraceptives and then monitor her blood pressure frequently.
Exactly why blood pressure rises as a result of taking oral contraceptives is unclear, but the amount of progesterone (not estrogen) in the preparation may be the problem. Preparations that contain less progesterone or intermittent progesterone are less often connected to high blood pressure in the patient.
If the blood pressure doesn’t return to normal when a woman discontinues the oral contraceptive, she should be evaluated for some other cause. A woman who can’t use another form of contraception may need to combine the oral contraceptive with a blood-pressure-lowering drug. (See article 13 for more information on pressure-lowering medications.)
Going past menopause
Unlike women who have not yet reached menopause, postmenopausal women — even those who have normal blood pressure — respond to stress with a rise in their blood pressure. The estrogen loss that occurs during menopause may not be the only factor; the weight gain that accompanies aging and other factors like diminished exercise may also contribute to the rise.
Note: Postmenopausal women are actually more sensitive to salt than men are, and this sensitivity may be an additional reason for their increased tendency towards high blood pressure.
Taking estrogenic hormones doesn’t seem to elevate blood pressure or make the postmenopausal woman more sensitive to salt or stress. For this reason, postmenopausal women who have high blood pressure may be given estrogens.
Rising in stages with age
Blood pressure tends to go up with age for many reasons — reduction in kidney function, less ability to rid the body of salt, hardening of the arteries, increasing obesity, and greater sensitivity to salt’s blood-pressure-raising effect.
With aging, the blood pressure tends to rise in stages. Although these stages vary for some individuals, high blood pressure usually develops in a fairly orderly fashion — from pre-high blood pressure to sustained high blood pressure.
High blood pressure can occur before age 30, but the usual sequence of events is as follows:
Between birth and the age of 30 (pre-high blood pressure stage):
Occasional blood pressure measurements may be high, but the elevation isn’t constant. However, even an occasional rise is a clue that high blood pressure may develop. Other clues are
- Birth weight is low.
- Blood pressure rises excessively during stress or exercise.
- Random pressure checks are high/normal (close to 140/90 mm Hg).
- Other features such as obesity, increased alcohol intake, diabetes, reduced HDL cholesterol, or increased triglycerides may be present.
Usually between the ages of 30 and 40:
This stage may last five to ten years. High blood pressure occurs frequently, but periods of normal blood pressure follow.
As early as 30 years of age, but usually by the age of 50 (essential hypertension — sustained high blood pressure for which the cause cannot be determined):
People who suffer from essential hypertension at age 50 or sooner are highly susceptible to early heart attacks and brain attacks. If left untreated, their life expectancy is reduced 15 to 20 years.
Past the age of 50:
This condition is more likely to be secondary (from other causes) high blood pressure, as I explain in article 4. Article 14 discusses the problems of blood pressure in the elderly at greater length.
Preventing High Blood Pressure with Lifestyle Changes
Every year, 2 million new patients are diagnosed with high blood pressure every year in the United States. Although you can’t change the genes that you received from your parents, you can change many lifestyle behaviors to prevent high blood pressure. For starters, all adults should be screened for high blood pressure at least every two years. Other changes you can make include:
- Reducing your stress using humor (see article 8)
- Increasing your potassium intake by eating more fruits and vegetables (see article 9)
- Reducing daily salt intake to less than 6,000 milligrams (1 teaspoon), which is equal to 2,400 milligrams of sodium (see article 10)
- Keeping alcohol intake to two drinks or less per day (see article 11)
- Controlling your weight through diet (see article 9) and exercise (see article 12)
All the techniques that prevent high blood pressure can also help lower blood pressure after it is present. But the greatest differences between prevention and treatment are the costs and risks of the medication that most people need to treat their high blood pressure. If you can prevent high blood pressure, do everything in your power to do so. You won’t be sorry.
Essential high blood pressure (see the previous section “Rising in stages with age”) is due equally to inheritance and the environment. The major factors in the environment are diet and psychological and social stresses. Many groups show the effects of stressful situations on blood pressure. For example:
- A study in the New England Journal of Medicine (March 1968) compared several nuns isolated in Italy to a group of women in regular society. Blood pressures were the same at the beginning, but after 30 years, the nuns’ blood pressures were 30 millimeters lower than the other group’s.
- People who go from low-stress societies (like the Nigerians in Africa that I describe in the previous section) to higher-stress societies (like Africans in America) show sustained increases in blood pressure.
- People who work in jobs where they have little control but much responsibility show elevated blood pressures.
- Air traffic controllers have higher blood pressures as a group than people in less stressful occupations.
- African Americans growing up in higher-stress environments have a higher incidence of high blood pressure.
Some of these studies have been questioned because of other contributing factors. For example, the diet of the nuns may have been less likely to cause high blood pressure, especially over 30 years. People going to higher-stress societies are also eating more salt than they did before.
Although some studies show a correlation between internalized anger, other studies don’t. Whether blood pressure tends to be high in certain individuals who turn their anger inward rather than responding by an external show of anger or some other external act (like increased exercise) is still the subject of much controversy.
Finally, do people who respond to stress by reacting excessively tend to develop high blood pressure more often than people who are less reactive? The answer isn’t clear; studies of this phenomenon are again inconsistent.
Many studies on stress and high blood pressure result in inconsistent findings, but one fact is certain: Reducing the level of stress in your life can only do you good. The less stressed you are, the less likely you are to overeat, smoke, and drink excessively — all factors known to cause high blood pressure. Article 8 introduces you to one great form of stress reduction — laughter.
Controlling your weight
The significance of an inactive lifestyle in the development of high blood pressure is clear. In study after study, people who exercise more have a lower incidence of high blood pressure, and active lifestyles promote weight control.
For every 10-pound weight gain, the systolic blood pressure goes up 4 to 5 millimeters of mercury. Therefore, you don’t have to be overweight or obese for weight gain to raise your blood pressure.
Central obesity (fat in the waist area) is associated with high blood pressure more than obesity in the legs and thighs. A large waistline is a good clue that high blood pressure is on its way or has already arrived.
The insulin resistance syndrome (We describe this condition earlier in the “Accounting for the contribution of your genes” section) contains factors that place the patient at high risk of heart disease:
- High blood pressure
- Elevated levels of insulin and insulin resistance
- Central distribution of fat
- High triglycerides
- Low HDL (good cholesterol) and higher levels of LDL (bad cholesterol)
- High levels of uric acid in the bloodstream
- Type 2 diabetes mellitus (formerly called non-insulin-dependent diabetes)
- High levels of chemicals that prevent clots from breaking down
Just how obesity results in higher blood pressure is unclear. But scientists do know the following:
- People who are obese have increased cardiac output (flow of blood from the heart) and increased peripheral resistance (resistance to the passage of blood through the arteries). As a result, more blood needs to be pumped to provide nutrients to their bodies’ increased tissues.
- Many organs, particularly the kidneys, don’t accept increased blood flow, so they produce hormones to reduce it by narrowing the arteries, thus increasing peripheral resistance and blood pressure.
- Obese people often take in more salt than lean people, and they’re more sensitive to the blood-pressure-raising effect of salt.
- Obesity is associated with an increase in the activity of the nervous system, which can cause narrowing of blood vessels.
In article 9, we recommend weight loss as one treatment of high blood pressure. Combined with exercise (which we discuss in article 12) and salt and alcohol reduction, weight loss can have a profound blood-pressure-lowering effect. Note: These measures should always precede pressure-lowering medications unless the blood pressure is dangerously high (greater than 180/120 mm Hg). Part of the positive effects of these lifestyle changes may include improvement in the insulin resistance syndrome, leading to reduced insulin and its role in raising blood pressure.
Using less salt
The typical diet throughout the wealthier nations of the world contains too much salt. Evidence abounds. Not all people, however, develop high blood pressure; only about half the population. So, people who have high blood pressure must have some form of increased sensitivity (salt raises their blood pressure to a greater extent). The evidence for the role of salt comes from population studies as well as experimental manipulation of salt intake. The population studies noted that:
- Primitive tribes that don’t eat salt have zero high blood pressure; they also don’t have the consequences of high blood pressure — damage to the heart, kidney, or brain.
- When these same primitive people eat salt, they develop high blood pressure and its consequences.
- The more salt consumed, the higher the blood pressure.
Experimental studies concluded that:
- When people with high blood pressure restrict their salt, they lower their blood pressure.
- Babies with a low-salt diet have lower blood pressures.
- Animals that consume more salt show a rise in blood pressure.
This sensitivity to salt seems to be inherited from the mother because she usually has the same rise in blood pressure as her offspring after eating salt. A person without salt sensitivity excretes most excess salt along with water in the kidneys, but a person with salt sensitivity can’t do this as easily.
Blood pressure, however, doesn’t always fall when salt is restricted because certain groups of people are more salt sensitive. These include:
- Older individuals
- People whose kidneys are failing
- People who don’t produce enough renin, an enzyme that raises blood pressure in their kidneys
Lowering your salt intake can help reduce your chances of developing high blood pressure. Paying attention to product labels and choosing foods labeled sodium-free or reduced-sodium can help you monitor your salt intake. We detail other practical ways to reduce your salt intake in article 10.
Cutting out smoking and excessive drinking
Using tobacco in any form and drinking excessively (see article 11) raise blood pressure, while the absence of smoking and drinking lowers blood pressure. Although tobacco and alcohol cause all kinds of other problems for you, their effect on your blood pressure is enough reason to stop using them.