Blood vessels stiffen with age, and this appears to be the primary cause of age-related hypertension, or raised blood pressure. That raised blood pressure in turn damages delicate tissues, increasing the pace at which ruptures occur in capillaries throughout the body. In the brain this causes many tiny, silent strokes over the years, adding up to create cognitive decline. Eventually hypertension combines with the corrosive effect of atherosclerosis on blood vessel walls to cause some form of fatal structural failure in a major blood vessel.
The causes of stiffening of blood vessels include cross-linking that disrupts the physical properties of the extracellular matrix, the related loss of elastin in the matrix, and dysfunction in the vascular smooth muscle cells responsible for constriction and dilation of blood vessels. That cellular dysfunction has a whole set of deeper causes, not all of which are well understood at this time. The chronic inflammation and harmful signaling generated by senescent cells seems to be involved, but it isn’t the whole story by any means.
Aging is associated with a progressive decline in vasoconstrictor responses in central and