Dietary Factors

L J Appel, Johns Hopkins University, Baltimore, MD, USA

© 2005 Elsevier Ltd. All rights reserved.

Worldwide, elevated blood pressure is an extraordinarily common and important risk factor for cardiovascular and kidney diseases. As blood pressure rises, so does the risk of these diseases (Figure 1). The relationship is strong, consistent, continuous, independent, and etiologically relevant. Accordingly, the adverse consequences of elevated blood pressure are not just restricted to individuals with hypertension (a systolic blood pressure >140 mmHg or a diastolic blood pressure >90 mmHg). Those with prehypertension, namely, a systolic blood pressure of 120-139 mmHg or diastolic blood pressure of 80-89 mmHg, have a high probability of developing hypertension and carry an excess risk of cardiovascular disease compared to those with a normal blood pressure (systolic blood pressure <120 mmHg and diastolic blood pressure <90 mmHg). In fact, almost one-third of blood pressure-related deaths from coronary heart disease occur in individuals with blood pressure in the nonhypertensive range.

In Western countries and most economically developing countries, systolic blood pressure rises with age. As a consequence, the lifetime risk of developing hypertension is extremely high, approximately 90% among US adults older than age 50 years. However, the rise in blood pressure with age is not inevitable. There are numerous isolated populations in which the rise in blood pressure is blunted or even flat. These populations are typically characterized by extremely low intakes of salt, relatively high intakes of potassium, and a lean body habitus.

Lifestyle modification, which includes dietary changes and increased physical activity, has important roles in both nonhypertensive and hypertensive individuals. In nonhypertensive individuals, including those with prehypertension, lifestyle modifications have the potential to prevent hypertension, reduce blood pressure, and thereby lower the risk of blood pressure-related cardiovascular disease. Even an apparently small reduction in blood pressure, if applied to an entire population, could have an enormous beneficial impact. It has been estimated that a 3 mmHg reduction in systolic blood pressure could lead to an 8% reduction in stroke mortality and a 5% reduction in mortality from coronary heart disease (Figure 2). In hypertensive individuals, lifestyle modifications can serve as initial

A: Systolic blood pressure

B: Diastolic blood pressure

Age at risk:

80-89 years

70-79 years

60-69 years

50-59 years

140 160 Usual systolic blood pressure (mm Hg)

Age at risk:

80-89 years

70-79 years

60-69 years

50-59 years

St ab g

Age at risk:

80-89 years

70-79 years

60-69 years

50-59 years

80 90 100 Usual diastolic blood pressure (mm Hg)

140 160 Usual systolic blood pressure (mm Hg)

Age at risk:

80-89 years

70-79 years

60-69 years

50-59 years

80 90 100 Usual diastolic blood pressure (mm Hg)

Figure 1 Stroke mortality rate by decade of age versus systolic blood pressure (A) and diastolic blood pressure (B): meta-analysis of 61 prospective studies with 2.7 million person-years. (Reprinted with permission from Lewington S, Clarke R, Qizilbash N, Peto R, and Collins R (2002) Prospective Studies Collaboration. Age-specific relevance of usual blood pressure to vascular mortality: a metaanalysis of individual data for one million adults in 61 prospective studies. Lancet 360: 1903-13.

mm Hg Stroke CHD Total

mm Hg Stroke CHD Total

Figure 2 Estimated effects of populationwide shifts in systolic blood pressure (SBP) on mortality. (Reprinted with permission from Stamler R (1991) Implication of the INTERSALT study Hypertension 17: I-16-I-20.)

treatment before the start of drug therapy and as an adjunct to medication in people already on antihypertensive drug therapy. In hypertensive individuals with medication-controlled blood pressure, lifestyle therapies can facilitate drug step-down and potentially drug withdrawal in individuals who sustain lifestyle changes.

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