Dementia of the Alzheimer’s type accounts for about 60 percent of old-age dementias. It is estimated to affect from 5 to 10 percent of people of age 65 years and accounts for the most striking increase in dementia incidence in very old individuals. Dementia of the Alzheimer’s type and related dementias cost society an estimated $100 billion each year, which includes both direct costs (i.e., actual dollar expenditures) and indirect costs (i.e., resource losses not involving dollar expenditures). The greatest risk factor for developing dementia is age. The incidence and prevalence of the disease double every 5 years after age 60 years. An estimated 4 million U.S. citizens have Alzheimer’s disease. As the Baby Boom generation (born in the 1950s and 1960s) moves into the age group of 60 years and older, Alzheimer’s disease will become an even greater public health problem. The number of Americans Alzheimer’s disease is expected to triple by mid-century, growing from 4.5 million to more than 13 million.

Although epidemiological studies show that anxiety disorders are less prevalent in older adults compared with younger adults, the prevalence of anxiety disorders in this older age group is high compared with that of other disorders. Indeed, anxiety disorders are the most prevalent psychiatric disorders, excluding the dementias, in people older than age 65 years. The most prevalent anxiety disorder among older adults is phobic disorder. Panic disorder is the least common anxiety disorder in this age group. Across all age groups, anxiety disorders are more prevalent in women than in men. The prevalence of anxiety disorders decreases with increasing age.

As a person ages, the optic lens thickens (not thins) in association with an inability to accommodate (presbyopia), and hearing loss is progressive, particularly at the high frequencies. The process of aging, known as senescence, results from a complex interaction of genetic, metabolic, hormonal, immunological, and structural factors acting on molecular, cellular, histological, and organ levels. The most commonly held theory is that each cell of the body has a genetically determined life span during which replication occurs a limited number of times before the cell dies. One study found 50 such replications in human cells. Structural changes in cells take place with age. In the central nervous system (CNS), for example, age-related cell changes occur in neurons, which show signs of degeneration.

A progressive decline in many bodily functions includes a decrease in melanin and decreases in cardiac output and stroke volume, glomerular filtration rate, oxygen consumption, cerebral blood flow, and vital capacity. Many immune mechanisms are altered, with impaired T-cell response to antigens and an increase in the formation of autoimmune antibodies. These altered immune responses probably play a role in aged persons’ susceptibility to infection and possibly even to neoplastic disease. Some neoplasms, most notably cancers of the colon, prostate, stomach, and skin, show a steadily increasing incidence with age.

Variable changes in endocrine function are seen. For example, postmenopausal estrogen levels decrease, producing breast tissue involution and vaginal epithelial atrophy. Testosterone levels begin to decline in the sixth decade of life; however, follicle-stimulating hormone and luteinizing hormone increase. In the CNS, there is a decrease in brain weight, ventricular enlargement, and neuronal loss of approximately 50,000 a day, with some reduction in cerebral blood flow and oxygenation.

In elderly persons, simple recall becomes difficult (does not remain intact), and memory-encoding ability diminishes. These functions decline with age. However, many cognitive abilities are retained in old age. Although elderly persons take longer than young persons to learn new material, complete learning of new material still occurs. Old adults maintain their verbal abilities, and their IQs remain stable until approximately age 80 years. On multiple-choice tests, recognition of correct answers persists.

Severe vitamin deficiencies in elderly adults are rare (rather than common). However, a number of conditions and deficiencies are typical and should be considered in the physical assessment of elderly patients. Toxins of bacterial origin and metabolic origin are common in old age. Bacterial toxins usually originate in occult or inconspicuous foci of infection, such as suspected pneumonic conditions and urinary infections. In elderly individuals, the most common metabolic intoxication causing mental symptoms is uremia

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