fourth or fifth leading cause of death in the United States (Weiler, 1987). Furthermore, in this country dementia now is the leading cause of institutionalization (Von Vostrand, 1979). Affective disorders are underreported in older persons even though they account for substantial disability in this age group (Finlayson and Martin, 1982). Although there are many outstanding research opportunities in this area, the greatest need is for studies linking basic and clinical approaches to the pathophysiology, cause, prevention, and treatment of Alzheimer 's disease and other dementias. Excellent opportunities are available for basic molecular and cell biologic studies to determine the mechanisms and causes of central nervous system cell death in the aged, particularly the role of growth factors in central nervous system changes associated with both normal aging and injury. These studies should include assessment of cellular and molecular markers and new approaches to imaging and neurotransmitter mapping of the nervous system. Such studies clearly overlap with the research areas emphasized in Chapter 2. In addition, clinical studies that focus on management strategies for demented older persons have major interrelations with social, behavioral, and health services research agendas.

Musculoskeletal Disorders

Musculoskeletal disorders rank second to circulatory system diseases as a cause of both disability and health care costs in the United States. These conditions rank second in frequency as a reason for visits to physicians and third in frequency of hospitalization. Osteoarthritis is the most prevalent joint condition after age 65 (National Center for Health Statistics, 1989), and ranks second (after cardiovascular disease) in producing severe disability in those over age 60. Osteoporosis is also extremely common; annually, over one million osteoporosis-related fractures occur in the United States (Resnick and Greenspan, 1989). Fractures of the vertebral bodies and the hip are the two most common types of fracture in elderly persons, and both cause significant morbidity. Of those suffering from hip fracture, 50 percent never walk again (Melton and Riggs, 1983). Resultant costs from these disorders total more than $65 billion annually.

The application of restriction fragment-length polymorphism and other techniques of reverse genetics will help to provide the tools necessary to define the genetic basis of osteoarthritis and osteoporosis in many patients suffering from these common disorders. Such approaches should receive a high priority, particularly if current



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