Intrinsic skin aging includes the inevitable physiologic changes of the skin that occur with time and are influenced by genetic and hormonal factors.
Extrinsic skin aging is the preventable structural and functional changes of the skin that occur with exposure to environmental factors, the most important source being ultraviolet radiation.
Intrinsic and extrinsic aging of the skin have distinct histologic and clinical manifestations.
Oxidative damage is a common component of the multiple mechanisms of aging.
Geriatric dermatoses include solar lentigines, seborrheic keratoses, senile angiomas, xerosis, asteatotic eczema, and pruritus.
There is increased incidence of benign and malignant skin growths in the elderly population.
Infections in the elderly often have distinctive causative organisms and increased morbidity and mortality relative to younger patients.
In Westernized countries, the chronologic age of older than 65 years is accepted as the definition of an elderly individual. By 2050, the elderly population is estimated to more than double in developing countries (World Health Organization. Global Health and Aging. 2011; http://www.who.int/ageing/publications/global_health/en/). This demographic transformation will present unique challenges to physicians across the medical specialties, including dermatology.
Aging is an inevitable and dynamic biologic process that is characterized by the progressive deterioration of many body systems and decline in physiologic reserve capacity. Given its location at the body’s environmental interface, human skin undergoes 2 distinct types of aging: intrinsic and extrinsic. Intrinsically aged skin appears dry and pale with fine wrinkles and increased laxity; whereas, photoaged skin is darker, coarser, and often has mottled pigmentation (Fig. 106-1). Intrinsic aging encompasses a set of gradual physiologic changes that are a consequence of time and under genetic and hormonal control. Conversely, extrinsic aging, also termed photoaging, includes dramatic structural and functional changes that are caused by exogenous factors, the primary one being unprotected sun exposure.
Difference between photoprotected and photoexposed skin.
OXIDATIVE STRESS AND AGING
One theory of aging involves cellular senescence or apoptosis secondary to oxidative damage.1 The generation of reactive oxygen species is a normal consequence of aerobic metabolism. Accordingly, a complex antioxidant system of enzymatic and nonenzymatic effectors has evolved to counteract the endogenously and exogenously produced free radicals in the skin (Table 106-1). However, the skin’s antioxidant defenses tend to weaken with age,2 and the resultant oxidative stress contributes to intrinsic aging.
Table 106-1The Antioxidant Systems of the Skin |Favorite Table|Download (.pdf) Table 106-1 The Antioxidant Systems of the Skin
|ENZYMATIC ||NONENZYMATIC |
|Glutathione peroxidase ||Vitamin C (ascorbic acid) |
|Catalase ||Vitamin E |
|Superoxide dismutase || |
Oxidative damage leads to the upregulation of stress-related factors, which can then trigger downstream events enabling the aging process. For example, stress-induced factors, such ...