What is blood pressure?

Blood pressure, measured with a blood pressure cuff and stethoscope by a nurse or other healthcare provider, is the force of the blood pushing against the artery walls. Each time the heart beats, it pumps blood into the arteries, resulting in the highest blood pressure as the heart contracts. One cannot take his own blood pressure unless an electronic blood pressure monitoring device is used. Electronic blood pressure monitors may also measure the heart rate, or pulse.

Two numbers are recorded when measuring blood pressure. The higher number, or systolic pressure, refers to the pressure inside the artery when the heart contracts and pumps blood through the body. The lower number, or diastolic pressure, refers to the pressure inside the artery when the heart is at rest and is filling with blood. Both the systolic and diastolic pressures are recorded as "mm Hg" (millimeters of mercury). This recording represents how high the mercury column is raised by the pressure of the blood.

High blood pressure, or hypertension, directly increases the risk of coronary heart disease (heart attack) and stroke (brain attack). With high blood pressure, the arteries may have an increased resistance against the flow of blood, causing the heart to pump harder to circulate the blood. According to the American Heart Association, high blood pressure for adults is defined as:

• 140 mm Hg or greater systolic pressure
  
  and/or
• 90 mm Hg or greater diastolic pressure

These numbers should be used as a guide only. A single elevated blood pressure measurement is not necessarily an indication of a problem. Your physician will want to see multiple blood pressure measurements over several days or weeks before making a diagnosis of hypertension (high blood pressure) and initiating treatment. A person who normally runs a lower-than-usual blood pressure may be considered hypertensive with lower blood pressure measurements than 140/90.

What are the risk factors for high blood pressure?

High blood pressure can occur in anyone, but is particularly prevalent in:

• persons with diabetes mellitus, gout, or kidney disease.
• African-Americans (particularly those who live in the southeastern United States).
• persons in their early to middle adult years; men in this age group have higher blood pressure more often than women in this age group.
• persons in their middle to later adult years; women in this age group have higher blood pressure more often than men in this age group (more women have high blood pressure after menopause than men of the same age).
• middle-aged and elderly people - more than half of all Americans age 65 and older have high blood pressure.
• persons whose parents or grandparents have/had high blood pressure.
• obese people.
• heavy drinkers of alcohol.
• women who are taking oral contraceptives.

How does blood pressure increase?

The following may contribute to an increase in blood pressure:

• being overweight
• excessive sodium intake
• a lack of exercise and physical activity

How is high blood pressure controlled?

Many people can control high blood pressure by:

• choosing foods that are low in sodium (salt).
• choosing foods low in calories and fat.
• choosing foods high in starch and fiber.
• maintaining a healthy weight, or losing weight if overweight.
• limiting serving sizes.
• increasing physical activity.
• practicing moderation if consuming alcoholic beverages.

However, other people must take daily medication to control hypertension. People with hypertension should routinely have their blood pressure checked and be under the care of a physician.

High blood pressure, obesity, and the risk for kidney cancer:

By themselves, hypertension and obesity are risk factors for a myriad of diseases, including heart disease and stroke. However, a new study now suggests that men who are both obese and suffer from high blood pressure may also be at greater risk for kidney cancer.

Obesity, as measured using the body mass index (BMI), is defined as an index of 30 or over. High blood pressure, according to the American Heart Association, is a systolic pressure of 140 mm Hg or higher and/or a diastolic pressure of 90 mm Hg or higher.

The study, published in the New England Journal of Medicine, reviewed health records and conducted follow-up checkups of more than 360,000 Swedish men from 1971 to 1995. The study found:

• Men whose body mass index ranged in the middle three-eighths of the group had 30 to 60 percent greater chance of developing renal-cell cancer (kidney cancer).
• High blood pressure appears to be directly associated with a higher risk of kidney cancer. Men with diastolic pressure of 90 mm Hg or more had double the risk of developing kidney cancer than men with diastolic pressure of less than 70 mm Hg. Men with systolic pressure of 150 mm Hg had a 60 to 70 percent greater chance of developing kidney cancer.
• Study participants who smoked or were former smokers were more likely to develop kidney cancer or renal-pelvis cancer.
• Lowering blood pressure lowered the risk of kidney cancer.
• Average body mass index for the participants was 24.5.
• A total of 759 men were diagnosed with kidney cancer.
• One-hundred thirty-six men were diagnosed with renal-pelvis cancer.
• Kidney cancer risk rose with increasing body mass index at each level of diastolic blood pressure.

The researchers eliminated statistics from men who were diagnosed with kidney cancer during the first five years of follow-up, because early stage renal tumors may increase blood pressure, contributing to the apparent increased risk from high blood pressure. However, even without those statistics, men with high blood pressure were still at considerably higher risk for kidney cancer than their healthier counterparts.

One explanation for the link between obesity and an increased risk for kidney cancer may be the higher levels of free insulin-like growth factor and free estrogens, which are linked to certain cancers, according to the researchers.

This study did not take into account the effects of antihypertensive drugs and diuretics, often used by people with high blood pressure, on the risk of kidney cancer. However, even with slight elevations in blood pressure (which do not require treatment), the study showed direct correlation between the higher blood pressure and risk for kidney cancer. More research will be needed to examine these associations, especially the apparent decrease in risk for kidney cancer when lowering high blood pressure.

Always consult your physician for more information.