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The Effects of Aging on Your Cardiovascular System
>An individual's ability to sustain a high level of exercise for a prolonged period of time decreases with age, even with healthy aging. This decline can be slowed by regular exercise, but it cannot be avoided completely. The decline is caused by a weakening of the functions of all the body's systems, though the focus here is on the heart.
>The heart has a pacing system that controls the heartbeat and regulates the electrical signals that stimulate the heart's pumping action. Over time, this natural pacemaker loses some of its cells, and some of its electrical pathways may get damaged. These changes can result in a slightly slower heart rate at rest and a greater susceptibility to abnormal rhythms (the most common of which is known as "atrial fibrillation").
>With increasing age, all the structures of the heart also become more rigid. The muscles of the left ventricle get thicker, the heart may increase slightly in size, and the volume of the left ventricle may decline. As a result, the heart may both fill and empty more slowly, thus putting less blood into circulation. The increase in one's heart rate and cardiac output in response to physical activity is also diminished, and one's maximum heart rate declines. The drop in maximum heart rate appears to be greater than average in sedentary individuals and in those with overt cardiovascular disease.
* The traditional formula for calculating maximum heart rate, proposed in the 1970s, was 220 less the individual's age.
>+ Tanaka and coauthors proposed an updated formula in 2001 for healthy nonsmokers of 208 less 7/10ths of the individual's age.
>Source: Modified from "Age-predicted maximal heart rate revisited" by H. Tanaka H et al. Journal of the American College of Cardiology; 2001; Vol. 37; pages 153-156.
>The autonomous nervous system changes with age, too. Normally, its parasympathetic component sets the level of the heart rate at rest, while its sympathetic component governs the heart in anticipation of and in response to physical activity — stimulating a timely and appropriate increase in blood flow to support the activity. Continuous adjustments between the sympathetic and parasympathetic systems result in minute variations in the heart rate (a factor known as "heart rate variability") that are evident on a beat-to-beat basis — the kind of sensitive regulation that is a signature of a healthy control system. With increasing age, however, the contribution of the parasympathetic system wanes; the sympathetic system's activity increases, even at rest; heart rate variability disappears; and the heart's rhythm becomes more prone to disruption. This age-related falloff in heart-rate variability and increase in resting heart rate (due to the decline in parasympathetic activity) are responsible for a 2.6-fold increased risk of SCD.