SKIN

Changes in the skin more obviously reflect the aging process than do changes in other organ systems (see Chap­ter 61). Aging can impinge on the primary functions of the skin: protection from the environment, temperature regu­lation, fluid and electrolyte balance, sensory function, and excretion of metabolic wastes. Exposure to sunlight and harsh weather accelerates aging of the skin.

With aging, the skin becomes wrinkled and dry and develops uneven pigmentation. The thickness of the der-mis, or middle layer of skin, decreases by approximately 20%, which gives the skin an overall thin and transparent quality. This is especially true for areas exposed to sunlight. Dermal collagen fibers rearrange and degenerate, resulting in decreased skin strength and elasticity. Cellularity and vascularity of the dermis decrease with advancing age and can cause vascular fragility, leading to senile purpura (i.e., skin hemorrhages) and slow skin healing. Delayed wound healing may be influenced by other factors such as poor nutrition and circulation and by changes in immune function.¹⁰,¹¹ The function of the sebaceous glands dimin­ishes with age and leads to a decrease in sebum secretion. The decrease in size, number, and activity of the eccrine sweat glands causes a decrease in their capacity to produce sweat.^10,11

Fingernails and toenails become dull, brittle, and thick, mostly as a result of decreased vascularity of the nail beds. Age-related changes in hair occur as well. Owing to a de­cline in melanin production by the hair follicle, approxi­mately one half of the population older than 50 years of age has at least 50% gray hair, regardless of sex or original hair color. Changes in hair growth and distribution also are seen.¹⁰,¹¹ Hair on the scalp, axillae, and pubis becomes more sparse, and the hairs of the ears and nostril coarsen. Skin disorders are common among the older adult popu­lation and can include skin cancers, keratoses (i.e., warty lesions), xerosis (i.e., excessive dryness), dermatitis, and pruritus (i.e., generalized itching).