How old are you? 20? 30? 60? Your answer will likely involve the number of years you’ve been alive — your chronological age.
Despite the cliche saying that “age is just a number”, it’s becoming quite reasonable to assume that this statement may in fact be true. How long you’ve lived doesn’t perfectly correlate with how well your body has aged. A new term for this has emerged — biological age. Biological age can be measured in several ways — measuring certain proteins in the blood or caps on the end of DNA (called telomeres) that shorten with age.
Our biological age tells us much more about our current state since it’s determined by factors other than just time. Biological age can be influenced by lifestyle habits like diet and exercise, environmental factors like pollution or sun exposure, and even stress. Negative lifestyle factors (smoking, poor diet, sedentary lifestyle) accelerate biological aging, while positive factors (exercise, fasting, even meditation) have been shown to slow or reverse biological aging.
One important aspect of biological aging involves the aging cardiovascular system. As we age, some major changes take place involving our blood vessels and our heart.
Specifically, with age, our vessels begin to get stiffer (less elastic). Arterial stiffness, as it’s known, causes extra stress to be placed on the heart and a resulting greater pressure throughout the cardiovascular system. This excess pressure gets transmitted into organs like the brain, kidney, and testicles, where it can damage small blood vessels and capillaries. Not good.
Arterial stiffness can also lead to poor blood vessel function — termed endothelial dysfunction. Together, these changes can place extra stress on our heart, leading to structural changes, worse heart function, and high blood pressure.
I’m particularly interested in exercise, and how it can influence the above maladaptive changes with aging. The evidence is abundantly clear that exercise (in this case, aerobic/endurance exercise) benefits several aspects of cardiovascular aging.
The direct effects of exercise on cardiovascular health might explain why high levels of physical activity are often associated with longevity. We haven’t had a study to directly show that exercise causes someone to live longer. But, by delaying cardiovascular aging, you’re preventing some of the biggest risk factors for death and disease from happening. When the cardiovascular system and aerobic capacity fail, everything else starts to fall apart.
Studies have shown that master’s athletes (or those who have engaged in lifelong exercise) are protected from much of the age-related increase in arterial stiffness. This happens in men and women. People who exercise more throughout life have less stiffness when you compare them to age-matched sedentary individuals.
In addition, if you take older sedentary individuals and put them through an exercise training regimen of just 8–12 weeks, they reverse their age-related arterial stiffness. While the levels aren’t quite equal to those of younger adults, they’re improved compared to sedentary levels in older adults. This suggest that, at least in terms of arterial stiffness, aging can be “reversed” by exercise.
The process of reversal makes sense from a “use it or lose it” perspective. When a dynamic blood vessel is continuously exposed to high levels of blood flow (like during exercise), it maintains it’s size and function; it adapts to the stimulus. However, with disuse, the artery gets stiff; it adapts to the (lack of ) stimulus.
Similar to stiffness, age-related endothelial dysfunction can also be reversed or prevented by exercise. In life-long exercisers, endothelial function is preserved with age. In fact, young adults and older exercise-trained adults have similar levels of endothelial function — suggesting exercise keeps artery health in a “young” phenotype. If you exercise sedentary adults, they can achieve levels of endothelial function similar to those of young adults. These effects are more profound than those for stiffness — which could only be partially preserved or reversed by exercise.
One caveat to the above summary. While the results of these training studies are consistently observed in older men, effects are less consistent in older postmenopausal women. That is, exercise training has been shown to have no effect on vascular function in older postmenopausal women.
Why is this? One hypothesis is that estrogen is necessary in order for exercise to exert its effects. Estrogen can act as an antioxidant in the cardiovascular system, and thus may play a role in “signaling” vascular adaptation to exercise. A loss of estrogen with menopause might put a limit on some of the exercise-associated cardiovascular benefits.
Exercise can improve endothelial function with age through one particular pathway. Exercise causes an increase in blood flow, leading to a release of a molecule called nitric oxide (NO) from the thin endothelial layer in our blood vessels. NO is a molecule that causes our blood vessels to vasodilate (relax). NO levels decline with age — and exercise can bring levels back to normal.
Exercise training can also reduce levels of oxidative stress and inflammation throughout the cardiovascular system, which further benefits stiffness and endothelial function.
Lower stiffness and improved vascular function are good in and of themselves, but synergistic effects on other organs and systems are a net beneficial side effect. The heart is placed under less stress, as are the kidneys and brain. Better kidney and brain function mean better health and a lower chance of experiencing age-associated diseases in these organs as well.
“Age-reversal” is a controversial word. No, we can’t literally turn back time, but it does seem like we can turn back the clocks inside our cells, returning them to a state that looks similar to a younger, maybe healthier version. Exercise is currently one of the most well-known ways to do this, and the evidence is pretty conclusive.
Seals DR, Nagy EE, Moreau KL. Aerobic exercise training and vascular function with ageing in healthy men and women. J Physiol (Lond). 2019;