As we age, main elements of our vascular system – the aorta, carotids, and other large arteries – that keep oxygen-rich blood flowing through our body start losing their capacity to widen or narrow. As Kevin Davy, a professor in the Department of Human Nutrition, Foods and Exercise at Virginia Tech University notes, “with agining, arterial compliance declines and arterial sitffness increases”. Arteries start stiffening at about age 30. Why arteries become less compliant as people age?
Damaged Endothelium
The endothelium is the inner lining of cells in all of the arteries in your body. It maintains the blood in a fluid state so that it does not clot. Endothelial cells are the place where eNOS – one of three isoenzymes of nitric oxide synthases – catalyze the production of nitric oxide (NO) from L-arginine. Nitric oxide is a sinalling molecula that relaxes and dilates blood vessels. Decline in production of NO results in less flexible arteries and decline in endothelial function that all togather contribute to the stiffness. If your endothelium is damaged you may be at risk of going to develop cardiovascular diseases with a possibility of heart failure, heart attack or stroke.
What causes the decline? Age and all of the other risk factors which lead to coronary heart disease also have been shown to hinder endothelial function. This is true no matter whether it is high blood pressure, diabetes, high cholesterol, being over weight, or not doing enough exercise, cigarette smoking. Nitric oxide not only relaxes and dilates blood bessels, but also prevents platelets and white boodcells from sticking to blood vessel walls. When an impaired artery lining produces less nitric oxide, it causes a vicious cycle: less NO leads to more plaque buildup in artery walls that means that the lining produces even less nitric oxide. This again leads to more plaque buildup in aretery walls.
The condition of endothelium reflects the health of your blood vessels- when endothelium is damaged, the development of arthersclerosis takes place that can lead to heart attack and stroke.
Rigid Arterial Walls
There are two main structural proteins in the large artery walls: collagen and elastin. Collagen provides the scafoolding that holds the arteries together, while elastin helps the blood vessels manage the flow of blood.
As people get older, collagen becomes more abundant in artery walls. And, over time, strands of collagen tend to bind (cross link) with other collagen strands. Both combine to make the large arteries more rigid.
If there is extra glucose (blood sugar) sloshing around, cross-linking speds up as the glucose binds to the collagen to form advanced glycation end-prodcuts or AGEs. Meanwhile, as we age, the elastin proteins stretch out and eventually start to rupture causing the arteries to lose even more flexibility.
Risk Associated with Arterial Stiffness
The modern scientific methods can now help to detect stiffening arteries long before any symptoms of disease appear. They can alert those who are on their way to develop cardiovascular disease. Apparently, many people of middle and advanced age whom we once thought to be healthy actually are not. It is becoming more evident that changes in the aging circulatory system, even without outward symptoms, precede a higher risk of developing cardiovascular diseases. The greater these changes, the greater is the risk of such diseases. These changes include the following health conditions:
High blood pressure
If your arteries are stiff that means your heart has to work harder to pump the blood out. It becomes part of the process that leads to heart failure, particularly in patients with high blood pressure.
Nine out of ten people will develop high blood pressure if they live long enough. Most of this is systolic hypertensions that is directly due to arterial stiffening.
Systolic pressure is the top number in a blood pressure reading: the maximum pressure on the arteries when the heart contracts and pushes blood out. Systolic high blood pressure was once thought to be a benign event therefore some primary care physicians did not even treat it. Not anymore!
It is now recognised that it needs to be controlled in middle-aged and older adults.
When arteries are stiff, blood pumped from the heart moves so quickly through them to the extremitites that the pulse wave that is generated bounces back to the heart while the heart is still contracting. That adds to the systolic pressure. Experts showed in the Baltimore Longitudinal Study of Aging that by using measurements of arterial stiffness you could predict the development of hypertension.
In the Baltimore Longitudinal Study of Aging Dr Edward Lakatta and his colleagues followed a group of 306 men and women over the next 12 year. Participants entered the study with normal blood pressure (roughly 115 over 75). A third of them developed hypertension while the two-thirds did not become hypertensive. The main difference between two groups was that the former had stiffer arteries when they entered the study.
Heart attacks & strokes
Arterial stiffness along side with a high level of LDL cholesterol are powerful predictors of future cardiovascular disease in older adults. The analysis of data from 17 international studies, tracking nearly 16,000 healthy men and women for an average of eight years, revealed that those who entered the studies with the stiffest arteries were twice as likely to later die from a heart attack or stroke.
Cognitive Degradation
The Baltimore Longitudinal Study of Aging also revealed that when your arteries cannot expand and contract easily, they cannot shield your smaller blood vessels from the regular high-pressure bursts of blood that the heart puts out. It was also suggested that this condition may damage your brain. People who entered the study cognitively intact but with stiffer arteries were more likely to show declines in verbal learning skills and memory over the next decade than those who started out with less stiff arteries.