How low should blood pressure be?

Epidemiological studies demonstrate a consistent linear association between level of diastolic or systolic blood pressure and cardiovascular risk, prediminantly in middle aged subjects. The risk of isolated systolic hypertension is also well established in middle aged and young elderly. In contrast, in the very elderly, studies provide conflicting evidence with J, U and even inverse relationships being reported. The EPESE study provides strong confirmation for the hypothesis that the association between blood pressure and mortality in later life is obscured by concurrent illness lowering blood pressure rather than a low pressure itself being a risk factor for mortality. Although there is consistent evidence that CHD events tend to increase at treated diastolic pressures below 85 mm Hg, it is unlikely that this is causally related since similar relationships are seen in patients on either placebo or control and probably reflect prior CHD. It appears reasonable to lower diastolic pressures to at least below 85 mm Hg. This gives maximum benefit for stroke reduction, while for myocardial infarction the rate is reduced compared to pressures over 100 mm Hg. Systolic pressure in middle aged fit hypertensive patients should be lowered to below 125 mm Hg since there is no indication of any adverse effects of so doing. There may however be subsets of patients in whom the effects of blood pressure lowering are uncertain, such as the very frail elderly or those with markedly reduced LV function.