Chapter 1.Epidemiology of Psychiatric Disorders in Later Life

The primary responsibility of clinical geriatric psychiatrists is to take care of their individual patients; why, then, should they concern themselves with the demography of aging in the population at large? Because the size, structure, distribution, and trends in the aging population are highly relevant to current and future clinical practice. Globally, including in the United States, the population is aging rapidly. The U.S. Census Bureau (2020) estimated that in 2020, about 56 million older adults were living in the United States and formed 17% of the total U.S. population. In 2030, as the current decade draws to a close, another 18 million older adults will be added to this segment, raising the proportion to 21% (Mather et al. 2015). This accelerated growth rate of older adults is driven by the aging of the Baby Boomers, born during the post–World War II “baby boom” between 1946 and 1964. The oldest Baby Boomers turned 65 years old in 2011, whereas the youngest will turn 65 in 2030. This demographic trend is not unique to the United States and other high-income countries. With substantial increases in life expectancy and declining fertility across the world, individuals older than 65 are now the fastest-growing segment in all world regions. They numbered 500 million (8%) in 2006 and will number 1 billion (13%, or one in every eight persons) in 2030 (National Institute on Aging et al. 2007). In fact, the most rapid increases in the older adult population are occurring in low- and middle-income countries, where there will be 140% growth between 2006 and 2030, compared with 51% in high-income countries.