Skin Age: A new wrinkle on an old biomarker

As a biomarker of aging, skin is something of a paradox. Normal skin aging hasn’t been shown to be associated with premature death as the disease processes of other organ systems are. But at the same time, no other organ confronts us with the aging process so viscerally. 
Skin presents an instant, visual indication of youthfulness and vitality–or accelerated aging. That assessment might be only skin deep, but for many people it’s deep enough. It can be an important factor in how they see their own aging—and in how old they feel. And it’s why there is an ever-exploding industry in skin-care products and cosmetic surgery.

But while we may think of wrinkles as the paradigm of aging, skin aging is actually not as plain to see as you might think. In fact, it’s just as slow and insidious as the aging of our arteries and lungs—a process that is far along by the time we see the most visible manifestations.

This similarity with the arterial and respiratory systems isn’t surprising. All three organs depend to a large degree on the integrity of their connective tissue—and that starts to change when we’re in our twenties.

So all the most common signs of aging that show up on the skin—wrinkling, sagging, discoloration—are manfestations of inflammation that degrades the collagen and elastin over time. These processes are set in motion years before they become visible, so that by the time you see sagging and wrinkling skin, it’s already at the end-stage of that aging process.

The unseen aging of the skin occurs deep in the dermis, where cells called fibroblasts make the structural fibers of connective tissue. Like other organs, the skin suffers from the oxidative stress of normal metabolic processes and the effects of declining hormone levels. But there’s one difference, and it’s a huge one.

The skin, of course is the only organ system that’s on the outside of the body (at least in part). So all the usual internal aging processes are compounded by the ultraviolet radiation we absorb from exposure—or overexposure—to the sun that starts when we’re young and becomes cumulative.

Put together, these external and internal factors upset the balance between breakdown and synthesis of the elements that give the skin its structural support.The consequences are hardly just cosmetic. Skin serves as the protective barrier between the internal organs and the outside environment, so how it ages has an impact on our overall health and aging.

There are two basic mechanisms of skin aging. One is called extrinsic or photo-aging because it affects only the parts of the body that are exposed to sun. So it varies by individual, depending on the degree and length of exposure. (Tobacco smoke and other environmental toxins can also be a factor in extrinsic aging.)

It’s the extrinsic aging that we see most when we look in the mirror. Studies have shown that facial skin appearance is affected more by exposure to the sun than by the passage of time. But because it doesn’t correlate with age, skin appearance is not a good biomarker of aging.

The other kind of skin aging correlates very closely with age—and only age. It’s called intrinsic or chronological aging. It happens to all the skin on the body as a result of internal metabolic processes, over time. It causes fine wrinkling and a loss of elasticity in areas that receive relatively little sun exposure. These effects are barely visible to the naked until they are relatively advanced. But there is a way to measure them with an instrument called a

Cutometer.

You may have seen or heard of an age-old age measurement commonly called a “pinch test,” in which you pinch the skin on the back of your hand, pull it up for a few seconds, then release it and count the seconds as it returns to its original flat position. The test shows that the skin of young people is thicker, firm enough that it can’t be pulled very far away from the bone, but supple enough to rapidly return to its original position. Though it’s a crude test, the skin pinch test illustrates one of the basic elements of how skin changes with age: It becomes thinner and therefore more easily extended.

A number of devices have been developed to measure changes in the mechanical properties of skin more precisely than a skin pinch test, but the Cutometer has emerged as the industry standard. It is used by many cosmetics and pharmaceutical companies to determine the effects of various topical and oral substances on the skin, and numerous papers have been published documenting its effectiveness.

The instrument works by substituting suction for pinching. A probe with a circular opening that varies in size from a tenth to a third of an inch is placed on the surface of the skin area to be measured. A suction pump attached to the other end generates a force that sucks the skin up into the probe chamber for a one-second interval and then releases the suction for one seconds.

This is repeated 20 times consecutively, and each timethe suction is applied to the skin an optical sensor measures how far and how fast it goes into and out of the probe chamber. Computer software then generates a graph of the distance the skin travels versus the time of the repetitions of suction and release.By involving only the top two layers of skin, the Cutometer non-invasively assesses the amount and structure of the collagen and elastins in your skin. The result is reported as a percentage of skin elasticity. The average person has almost 90 percent elasticity at the end of adolescence and typically loses 1 percent a year after that.

Hundreds of studies over the past 25 years have validated the instrument to the degree that its measurements can be considered a reliable biomarker of aging. The studies have confirmed that as skin ages, it becomes less elastic, more plastic, and more vulnerable to fatigue. These gradual alterations in the mechanical properties of the skin, particularly in the dermis, are precursors to the visible signs of aging—wrinkling, sagging, discoloration.

The Cutometer’s elasticity readings have also been correlated with bone density.The measurements can track changes and assess whether therapies aimed at slowing or reversing skin aging are working. For instance, hormone replacement therapy has been shown to improve skin elasticity in women. But like all clinical studies, it is a broad brush. The biomarker of a Cutometer measurement provides more precise and objective evidence of whether the therapy is having that beneficial effect in a particular individual.