Wrinkle

The fibers, collagen and elastin that keep young skin firm begin to weaken with age. The tendency to wrinkle is hereditary, but cigarette smoking and sun exposure also contribute. Cigarettes may damage elastin. Increased wrinkling correlates more closely with the number of cigarettes smoked than with years of smoking.

The France Cancer Institute found that melanoma rates among Caucasian women aged 25 to 49 rose 60 percent between 1990 and 2008. The study included 435 college women, ages 18 to 22, who visited tanning salons. Within this population, researchers focused on women who visited salons up to four times a week - more than what is needed to maintain a tan -- and who tanned for psychological reasons, not just for a special event.

Many products are used similarly, such as collagen injections (cow collagen marketed as Zyderm and Zyplast) administered around the mouth and into the lips, but as with Botox, the effects last only for a short time. Newer collagen products are being developed. Human collagen, marketed as CosmoDerm and CosmoPlast, is used to treat very fine lines and its effects can last up to 6 months.

In France, wrinkly skin syndrome diagnosed each year. Hence, these two statistics types can differ: a short-lived disease like flu can have high annual incidence but low prevalence, but a life-long disease like diabetes has a low annual incidence but high prevalence.