Risk factors for reduced skin thickness and bone density: possible clues regarding pathophysiology, prevention, and treatment.

The decline in skin thickness that occurs with aging interests many different groups. Among these are pharmaceutical, cosmeceutical, and cosmetic companies promoting antiaging or antiwrinkling products, geriatricians and rheumatologists treating elderly and steroid-dependent patients who are "outliving" their skin, cosmetic surgeons, and dermatologists. Dermatologists are frequently asked how to prevent or slow aging of the skin. The answer regarding "photoaging" of sun-exposed skin is obvious; the answer regarding aging of photoprotected skin is not. Although the bulk of epidemiologic literature about aging and thinning of photoprotected skin is from the 1970s, literature regarding risk factors for and treatment of aging and thinning of the bony skeleton is more recent. Because both skin and bone are composed of more than 70% type I collagen, it may be hypothesized that the pathophysiologic processes involved in chronological atrophy of both tissues may overlap, thereby providing a foundation for further investigation of the skin. A better understanding of skin and bone loss may motivate the "appearance-conscious" public to modify risk factors (e.g., begin exercising) or select hormonal therapies (e.g., postmenopausal hormone replacement) to reduce aging of the skin. These measures may provide additional benefits, such as decreasing the risk of osteoporosis.