Sex, age, and neurovascular control

In this chapter we focus on how age and sex affect blood pressure in humans. Our key concept, based on work primarily from our lab, is that sex differences in blood pressure regulation are due to differences in the transduction of sympathetic activity into vascular resistance that differ in women and men. In men (at least from low activity, high calorie countries) blood pressure drifts upward with time. In women blood pressure is lower than men until middle age when at menopause it rises more sharply than men. By the 7th decade of life more women are hypertensive than men. The lower blood pressure in women earlier in life can be explained in part because the vasoconstricting actions of sympathetic activity and norepinephrine are offset by concurrent β-adrenergic vasodilation. This dilation is lost around menopause and together with age-related increases in sympathetic activity these phenomenon can explain much of the rise in blood pressure seen in women as they age. By contrast, while sympathetic activity also rises in men as they age, their blood vessels become less sensitive to the vasoconstricting actions of norepinephrine. We discuss these findings and also consider how changes in cardiac output and endothelial function influence them.