The world is on the brink of a demographic milestone. Since the beginning of recorded history, young children have outnumbered their elders. In about five years’ time, however, the number of people aged 65 or older will outnumber children under age 5. Driven by falling fertility rates and remarkable increases in life expectancy, population aging will continue, even accelerate (Figure 1). The number of people aged 65 or older is projected to grow from an estimated 524 million in 2010 to nearly 1.5 billion in 2050, with most of the increase in developing countries.
The remarkable improvements in life expectancy over the past century were part of a shift in the leading causes of disease and death. At the dawn of the 20th century, the major health threats were infectious and parasitic diseases that most often claimed the lives of infants and children. Currently, noncommunicable diseases that more commonly affect adults and older people impose the greatest burden on global health.
In today’s developing countries, the rise of chronic noncommunicable diseases such as heart disease, cancer, and diabetes reflects changes in lifestyle and diet, as well as aging. The potential economic and societal costs of noncommunicable diseases of this type rise sharply with age and have the ability to affect economic growth. A World Health Organization analysis in 23 low- and middle-income countries estimated the economic losses from three noncommunicable diseases (heart disease, stroke, and diabetes) in these countries would total US$83 billion between 2006 and 2015.
Source: United Nations. World Population Prospects: The 2010 Revision. Available at: http://esa.un.org/unpd/wpp .
Reducing severe disability from disease and health conditions is one key to holding down health and social costs. The health and economic burden of disability also can be reinforced or alleviated by environmental characteristics that can determine whether an older person can remain independent despite physical limitations. The longer people can remain mobile and care for themselves, the lower are the costs for long-term care to families and society.
Because many adult and older-age health problems were rooted in early life experiences and living conditions, ensuring good child health can yield benefits for older people. In the meantime, generations of children and young adults who grew up in poverty and ill health in developing countries will be entering old age in coming decades, potentially increasing the health burden of older populations in those countries. With continuing declines in death rates among older people, the proportion aged 80 or older is rising quickly, and more people are living past 100. The limits to life expectancy and lifespan are not as obvious as once thought. And there is mounting evidence from cross- national data that—with appropriate policies and programs—people can remain healthy and independent well into old age and can continue to contribute to their communities and families.
The potential for an active, healthy old age is tempered by one of the most daunting and potentially costly consequences of ever-longer life expectancies: the increase in people with dementia, especially Alzheimer’s disease. Most dementia patients eventually need constant care and help with the most basic activities of daily living, creating a heavy economic and social burden. Prevalence of dementia rises sharply with age. An estimated 25-30 percent of people aged 85 or older have dementia. Unless new and more effective interventions are found to treat or prevent Alzheimer’s disease, prevalence is expected to rise dramatically with the aging of the population in the United States and worldwide.
Aging is taking place alongside other broad social trends that will affect the lives of older people. Economies are globalizing, people are more likely to live in cities, and technology is evolving rapidly. Demographic and family changes mean there will be fewer older people with families to care for them. People today have fewer children, are less likely to be married, and are less likely to live with older generations. With declining support from families, society will need better information and tools to ensure the well-being of the world’s growing number of older citizens.