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Over the past century, there have been truly remarkable changes in the numbers and characteristics of older persons throughout the world. The growth of the older population has resulted from a general increase in the overall population size but has been particularly affected by major declines in several of the leading causes of mortality. The increased survival of older persons has also been accompanied by declining birth rates; so the proportion of the population aged 65 years and older has increased dramatically and will continue to increase for the next 50 years. These demographic transformations have an effect on society that reverberates well beyond the increased medical care needs associated with an older population.

As more people live to advanced old age, it is important to gain a greater understanding of more than just the individual diseases that affect them. It is critical to appreciate the global picture of older persons who may have multiple chronic conditions, decrements in functional abilities, and social and psychological problems that may have an impact on many facets of their health and quality of life. In contrast to the previous stereotype, older people become more heterogeneous, not more alike, as they age, and understanding this process is a key challenge of geriatric medicine. Adding to the clinical perspective on single patients or small samples of patients, geriatric epidemiology has provided a useful tool with which to approach these challenges by studying representative populations of older persons. Going beyond the demographic focus of counting and projecting the number of older people in the population, epidemiology has made additional contributions to our understanding of the health status and functional trajectory of the older population. Since the 1980s, epidemiologic researchers either have utilized previously initiated cohort studies that include persons who have aged during the study or have begun new cohorts focusing on older people. These epidemiologic studies have assessed the distribution and determinants of specific diseases and have evaluated issues of relevance to an aging population, such as quality of life, geriatric syndromes, comorbidity, functional status, and end-of-life issues. Many of the chapters in this book refer to epidemiologic research on specific diseases and conditions. This chapter focuses on the more general or “geriatric” outcomes, particularly disability, that have also been the subject of much epidemiologic investigation.

The chapter begins by documenting the rapid growth and impressive increases in the number of older persons in the United States and other countries. It then examines improvements in survival and life expectancy. Selected demographic characteristics are then considered, including living situation and labor force participation across many developed countries.

The second section, on mortality, depicts current causes of death in the older population in the United States and considers the change in death rates with increasing age. Data on overall and disease-specific changes in mortality rates from 1950 through 2004 show the dramatic changes in these rates. The third section addresses chronic disease in the older ...

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