Shelby Scott, M.D., FACSM, is part-time faculty at Natividad Medical Center in Salinas, CA, and associate clinical faculty at University of California-San Francisco School of Medicine. She practices Family Practice and Sports Medicine in the Santa Cruz area of California.
Blood pressure is the term used to define the pressure exerted by blood on the inner walls of the arteries. It is measured as two values: the arterial pressure as the heart contracts, then the pressure as the heart relaxes or fills with blood. These are known as the systolic and diastolic pressures, respectively. Hypertension (HTN) is the medical term for high blood pressure (Table 1). It affects 50 million adults in the U.S. or approximately 25% of the population (1). Worldwide, more than 1 billion people have HTN, with 7.1 million deaths directly related to elevated blood pressure (2). The adverse effects of elevated blood pressure, including heart and kidney disease, are cumulative. To reduce lifetime risk of coronary disease, people with pre-HTN and HTN should be followed medically. Recent studies have shown that cardiovascular disease risk doubles for each 20/10-mmHg measure of blood pressure over 115/75 mmHg (3).
Blood pressure varies over the course of the day, increasing with the physical exertion required for daily activities. Average pressures also increase because of stress (4). Therefore, before a diagnosis of HTN is assigned to a person, the pressure must be elevated on at least two separate occasions, measured with the person seated and after rest (1). As we age, the blood vessels lose their elasticity. This results in stiffer vessels and higher pressures within the vessels. Long-term studies have shown that 90% of people over 55 years old who do not have HTN will develop it over the course of their lifetime (2,3).
Untreated HTN can lead to serious health complications. As previously mentioned, the effects are cumulative. Elevated blood pressure puts extra strain on the arteries and the heart. The heart exerts extra force to pump blood through the high-pressure system. This leads to heart enlargement and eventual failure, kidney damage, myocardial infarction, and stroke. To prevent these adverse effects, it is imperative to lower the blood pressure to near normal levels. People with pre-HTN can prevent heart disease when the pressure is lowered to normal values. For others with confounding medical illnesses like diabetes or preexisting kidney disease, there is evidence to support starting pharmacological intervention at the pre-HTN levels.
Poor diet and physical inactivity are associated with elevated blood pressure. Therefore, simple dietary changes and weight loss are effective measures for lowering blood pressure (4). These are called nonpharmacological measures or measures that do not involve drugs. Other nonpharmacological measures that can lower blood pressure are smoking cessation, stress reduction, reduced alcohol consumption, and regular exercise.
Switching from a high-sodium diet to a low-sodium diet results in lower blood pressure. The average American eats 4,000 mg of sodium per day. In countries where the average intake is less than 1,000 mg daily, the incidence of HTN is very low. A low-sodium diet can effectively lower blood pressure in people who have HTN and borderline HTN. Reducing the daily sodium intake helps to maintain a normal blood pressure in people who stop their antihypertensive medications based on their blood pressure measurements. Reduced sodium also can increase the efficacy of blood pressure treatment medicines. Reducing sodium from 4,000 to 2,000 mg can lower blood pressures by 2 to 3 mmHg in people with normal blood pressure (5) (Table 2). Although most people find it difficult to abruptly cut their salt intake in half, gradually decreasing salt intake and choosing fresh over prepared foods can be done easily. The medical effects of a low-salt diet are evident after 6 weeks and, with time, may result in a reduction in blood pressure of as much 10 mmHg.
Another dietary measure to lower blood pressure is increasing fiber. Adding fiber supplements to a person's existing diet can lower the blood pressure by 1.2 mmHg systolic/1.3 mmHg diastolic daily. Eating a well-balanced diet low in total and saturated fa4s has the same effect. Increasing intake of fresh fruits and vegetables can lower the blood pressure by increasing the fiber.
Regular physical activity is even more effective than dietary changes in the lowering of blood pressure. Regular exercise can lower blood pressure by up to 15 mmHg (6). In people older than 65 years, the effects are less pronounced (7). As with dietary changes, the effects are transient. If a person resumes a sedentary lifestyle, the pressure returns to the preintervention levels. As activity increases, most people will have a resultant loss of weight. Increased weight alone leads to elevated blood pressures. For every kilogram (2.2 lbs) of weight lost, the blood pressure falls by approximately 1 mmHg.
The most efficient exercise regimen for reducing blood pressure is one with moderate aerobic activity. In fact, the intensity of the exercise is more important than the frequency. A vigorous program 2 to 3 times a week can lower blood pressure almost as much as moderate activity every day. The ideal program includes moderate-to-vigorous cardiovascular activity on most days of the week (4). The response also is dependent upon continuation of the activity. All physical activity lowers the risk of cardiovascular disease and events. Even adding 10 minutes of exercise daily can lower risk of heart disease (4). Swimming is an effective form of aerobic exercise for people with osteoarthritis and other orthopedic problems. Even nonaerobic activity like moderate intensity weightlifting can lead to lower average blood pressures.
Exercise, especially a vigorous exercise regimen, can result in myocardial infarction (heart attack) or cardiac death. This occurs in people most at risk, and subsequently most in need, of increased physical activity. Those at highest risk are sedentary people starting a vigorous exercise program. Cardiac events can be prevented by gradually increasing both the frequency and the intensity of the exercise program. The benefits of a regular program of aerobic exercise are well documented, and people with most diseases will benefit from increased activity.
In summary, with 7.1 million deaths attributed to HTN in the world every year, it is important to use lifestyle modifications to prevent HTN. Increased exercise combined with dietary changes is often efficacious in lowering blood pressure in people with pre-HTN. The same measures also help lower the blood pressure in people needing pharmaceutical intervention. The incidence of HTN will increase as obesity increases worldwide. Therefore, dietary and other lifestyle modifications are important population issues for the prevention of HTN and resultant heart disease.
2. World Health Report 2002: reducing risks and promoting healthy lifestyles. Geneva, Switzerland: World Health Organization, 2002. Available at: http://www.who.int/whr/2002/
. Accessed February 1, 2007.
3. Hajjar, I., and T.A. Kotchen. Trends in prevention, awareness, treatment, and control of hypertension in the US, 1988-2000. Journal of the American Medical Association
5. Sacks, F.M., L.P. Svetkey, W.M. Vollmer, et al. Effects on blood pressure of reduced dietary sodium and the dietary approaches to stop hypertension (DASH) diet. DASH-Sodium Collaborative Research Group. New England Journal of Medicine
6. Duncan, J.J., J.E. Farr, S.J. Upton, et al. The effects of aerobic exercise on plasma catecholamines and blood pressure in patients with mild essential hypertension. Journal of the American Medical Association
7. Stewart, K.J., A.C. Bacher, K.L. Turner, et al. Effect of exercise on blood pressure in older persons: a randomized controlled trial. Archives of Internal Medicine