If you look at a U.S. president prior to him taking office with his looks after four or eight years on the job and it's hard to avoid the conclusion that stress affects aging.

Much as any manufactured product such as a car, an appliance, roads, etc. - our bodies are susceptible to wear and tear. Major organs such as the heart, liver, and kidney are critical parts of the human body. And constant wear and tear on them has an additive effect. When our bodies are stressed, the heart rate increases, the blood pressure goes up, and our adrenal glands flood our bloodstream with hormones. If this series of events happens only once in a while, no real harm is done to the body. But if the stress is ongoing, real damage begins to happen to the components inside of our bodies.

A perfect example is the starter switch of an automobile. Every starter switch in an automobile has a pretty much pre-determined life span. On an average day of driving our car we might start our car by turning on the starter switch 3 to 7 times a day. We do it when we go to work, when we return home, possibly during the course of running errands throughout the day. This is normal use and our starter switch will last for years under normal use. Now imagine how long that switch would last if you were to turn your car on, but instead of releasing the ignition switch when your car starts, you continue to turn your starter switch. You'll be lucky if the starter switch lasts a day.

Well, habitual stress in our bodies has a related effect. Biologists have theorized that, similar to that starter switch, each cell in the human body has a programmed and pre-determined life span. And when that life span has expired, the cell chromosomes will no longer work and the cell will die. When the body is under prolonged stress. it is persistently activating the "fight-or-flight" responses in the body. Said differently, the starter switch has been turned on and left on. The theory is that it is this constant stress that ages the body. But how? The answer is the telomere.

A telomere is a scientific term specifying a region of repetitive DNA at the end of chromosomes. It protects the end of the chromosome from destruction. The telomere is also involved in the replication of cells. Each time a cell divides, the telomere is shortened. Eventually the length of the telomere becomes so short that it can no longer divide. At this point the cell dies. Recent studies have shown that chronic stress tends to accelerate the shortening and shriveling of the telomere, directly causing the body to age faster. The greater the level of chronic stress, the faster the body's cells die and the faster the body gets wrinkles, weakened muscles, frailer bones, poorer eyesight, and other typical signs of aging.

Scientist can now actually measure a cell's age by looking at its chromosomes. This means that they can measure, at a cellular level, the damage that stress is having on the cell's chromosomes. Though more studies are needed to confirm this, one theory is that it is the high levels of stress hormones in the body, particularly cortisol, that is doing damage to the telomeres.

For a long time there has been an association between chronic stress and increased risk of major chronic diseases such as high blood pressure, heart disease, and diabetes. There now appears to be a direct link, as well, between chronic stress and premature aging in otherwise healthy people.