Understanding Aging Skin
Research shows that there are, in fact, two distinct types of aging. Aging caused by the genes we inherit is called intrinsic (internal) aging. The other type of aging is known as extrinsic (external) aging and is caused by environmental factors, such as exposure to the sun’s rays.
Intrinsic aging, also known as the natural aging process, is a continuous process that normally begins in our mid-20s. Within the skin, the dermis of normal (wrinkle-free) skin is composed of abundant amounts of type I collagen and type VII collagen, as well as elastin, which provide tissue strength, resiliency and recoil. The skin cells in the dermis also produce hyaluronic acid, a sugar complex that traps and holds water in the skin and which gives the skin “cushioning” and provides a supple and soft appearance. As dermal fibroblasts begin to age, they produce decreasing amounts of collagen and elastin. Further, aging fibroblasts produce increased amounts of enzymes called matrix metaloprotienases (MMP’s), which degrade collagen and elastin. This “aging” process results in a drastic loss of collagen and elastin over time and results in skin laxity and fragility, visible in the form of fine lines and wrinkles. The signs of intrinsic aging are:
- Fine wrinkles
- Thin and transparent skin
- Loss of underlying fat, leading to hollowed cheeks and eye sockets as well as noticeable loss of firmness on the hands and neck
- Dry skin that may itch
Genes control how quickly the normal aging process unfolds. For example, in regard to graying hair, some notice those first gray hairs in their 20s; others do not see graying until their 40s.
In extrinsic aging, a number of external factors often act together with the normal aging process to prematurely age our skin. Most premature aging is caused by sun exposure. Other external factors that prematurely age our skin are repetitive facial expressions, gravity and smoking.
Without protection from the sun’s rays, just a few minutes of exposure each day over the years can cause noticeable changes to the skin. Freckles, age spots, spider veins on the face, rough and leathery skin, fine wrinkles that disappear when stretched, loose skin, a blotchy complexion and skin cancer can all be traced to sun exposure.
“Photoaging” is the term dermatologists use to describe this type of aging caused by exposure to the sun’s rays. The amount of photoaging that develops depends on: 1) a person’s skin color and 2) their history of long-term or intense sun exposure. People with fair skin who have a history of sun exposure develop more signs of photoaging than those with dark skin. In the darkest skin, the signs of photoaging are usually limited to fine wrinkles and a mottled complexion.
Photoaging occurs over a period of years. With repeated exposure to the sun, the skin loses the ability to repair itself, and the damage accumulates. Scientific studies have shown that repeated ultraviolet (UV) exposure impairs the synthesis of new collagen and increases the expression of MMP enzymes, which break down collagen. The sun also causes changes and breaks in elastin, leading to a condition referred to by dermatologists as elastosis. Due to the loss of collagen and changes to the organization of elastin, sun-weakened skin ceases to spring back compared to skin protected from UV rays. The skin becomes loose, wrinkled, and leathery much earlier in life when the skin has been exposed to the UV rays of sunlight wihout adequate sun protection.