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Public Health and Aging: Trends in Aging --- United States and Worldwide

The median age of the world's population is increasing because of a decline in fertility and a 20-year increase in the average life span during the second half of the 20th century (1). These factors, combined with elevated fertility in many countries during the 2 decades after World War II (i.e., the "Baby Boom"), will result in increased numbers of persons aged >65 years during 2010--2030 (2). Worldwide, the average life span is expected to extend another 10 years by 2050 (1). The growing number of older adults increases demands on the public health system and on medical and social services. Chronic diseases, which affect older adults disproportionately, contribute to disability, diminish quality of life, and increased health- and long-term--care costs. Increased life expectancy reflects, in part, the success of public health interventions (2), but public health programs must now respond to the challenges created by this achievement, including the growing burden of chronic illnesses, injuries, and disabilities and increasing concerns about future caregiving and health-care costs. This report presents data from the U.S. Bureau of the Census, the World Health Organization, and the United Nations on U.S. and global trends in aging, including demographic and epidemiologic transitions, increasing medical and social costs related to aging, and the implications for public health.

U.S. Trends

In the United States, the proportion of the population aged >65 years is projected to increase from 12.4% in 2000 to 19.6% in 2030 (3). The number of persons aged >65 years is expected to increase from approximately 35 million in 2000 to an estimated 71 million in 2030 (3), and the number of persons aged >80 years is expected to increase from 9.3 million in 2000 to 19.5 million in 2030 (3). In 1995, the most populous states had the largest number of older persons; nine states (California, Florida, Illinois, Michigan, New Jersey, New York, Ohio, Pennsylvania, and Texas) each had more than one million persons aged >65 years (4). In 1995, four states had >15% of their population aged >65 years; Florida had the largest proportion (19%) (5). By 2025, the proportion of Florida's population aged >65 years is projected to be 26% (5) and >15% in 48 states (all but Alaska and California) (5).

The sex distribution of older U.S. residents is expected to change only moderately. Women represented 59% of persons aged >65 years in 2000 compared with an estimated 56% in 2030 (3). However, larger changes in the racial/ethnic composition of persons aged >65 years are expected. From 2000 to 2030, the proportion of persons aged >65 years who are members of racial minority groups (i.e., black, American Indian/Alaska Native, Asian/Pacific Islander) is expected to increase from 11.3% to 16.5% (4); the proportion of Hispanics is expected to increase from 5.6% to 10.9% (4).

Global Trends

In 2000, the worldwide population of persons aged >65 years was an estimated 420 million, a 9.5 million increase from 1999 (2). During 2000--2030, the worldwide population aged >65 years is projected to increase by approximately 550 million to 973 million (3), increasing from 6.9% to 12.0% worldwide, from 15.5% to 24.3% in Europe, from 12.6% to 20.3% in North America, from 6.0% to 12.0% in Asia, and from 5.5% to 11.6% in Latin America and the Caribbean (2). In Sub-Saharan Africa, an area where both fertility and mortality rates are high, the proportion of persons aged >65 years is expected to remain small, increasing from an estimated 2.9% in 2000 to 3.7% in 2030 (2). The largest increases in absolute numbers of older persons will occur in developing countries*. During 2000--2030, the number of persons in developing countries aged >65 years is projected to almost triple, from approximately 249 million in 2000 to an estimated 690 million in 2030 (3), and the developing countries' share of the world's population aged >65 years is projected to increase from 59% to 71% (2). However, migration patterns could influence these projections.

The aging of the world's population is the result of two factors: declines in fertility and increases in life expectancy (2). Fertility rates declined in developing countries during the preceding 30 years and in developed countries throughout the 20th century (2). In addition, in developed countries, the largest gain ever in life expectancy at birth occurred during the 20th century, averaging 71% for females and 66% for males (2). Life expectancy at birth in developed countries now ranges from 76 to 80 years (2). Life expectancy also has increased in developing countries since 1950, although the amount of increase varied. A higher life expectancy at birth for females compared with males is almost universal. The average sex differential in 2000 was approximately 7 years in Europe and North America but less in developing countries (2).

Demographic Transition

The world has experienced a gradual demographic transition from patterns of high fertility and high mortality rates to low fertility and delayed mortality (2). The transition begins with declining infant and childhood mortality, in part because of effective public health measures (2). Lower childhood mortality contributes initially to a longer life expectancy and a younger population. Declines in fertility rates generally follow, and improvements in adult health lead to an older population. As a result of demographic transitions, the shape of the global age distribution is changing. By 1990, the age distribution in developed countries represented similar proportions of younger and older persons (Figure) (2). For developing countries, age distribution is projected to have similar proportions by 2030 (2).

Epidemiologic Transition

The world also has experienced an epidemiologic transition in the leading causes of death, from infectious disease and acute illness to chronic disease and degenerative illness. Developed countries in North America, Europe, and the Western Pacific already have undergone this epidemiologic transition, and other countries are at different stages of progression. In 2001, the leading causes of death in developed countries, which had low child and delayed adult mortality, were primarily cardiovascular diseases and cancer, followed by respiratory diseases and injuries (6). The leading causes of death in African countries, which had high child and adult mortality, were infectious and parasitic diseases (e.g., human immunodeficiency virus/acquired immunodeficiency syndrome, malaria, childhood diseases, and diarrheal disease), respiratory infections, perinatal conditions, cardiovascular diseases, cancer, and injuries (6).

The epidemiologic transition, combined with the increasing number of older persons, represents a challenge for public health. In the United States, approximately 80% of all persons aged >65 years have at least one chronic condition, and 50% have at least two (7). Diabetes, which causes excess morbidity and increased health-care costs, affects approximately one in five (18.7%) persons aged >65 years, and as the population ages, the impact of diabetes will intensify (7). The largest increases in diabetes are expected among adults aged >75 years, from 1.2 million women and 0.8 million men in 2000 to 4.4 million women and 4.2 million men in 2050 (8). As U.S. adults live longer, the prevalence of Alzheimer's disease, which doubles every 5 years after age 65, also is expected to increase (7). Approximately 10% of adults aged >65 years and 47% of adults aged >85 years suffer from this degenerative and debilitating disease (7).

Chronic conditions also can lead to severe disability. For example, in the United States, arthritis affects approximately 59% of persons aged >65 years and is the leading cause of disability (9). However, some studies have shown that disability can be postponed through healthier lifestyles (10). Disability among older U.S. adults, as measured by limitations in instrumental activities of daily living, has declined since the early 1980s (11). Disability also is measured by limitations in activities of daily living (ADL), a common factor leading to the need for long-term care (11). Recent studies using ADL measures have shown varied trends in disability (11).

Impact on Medical and Social Services

The increased number of persons aged >65 years will potentially lead to increased health-care costs. The health-care cost per capita for persons aged >65 years in the United States and other developed countries is three to five times greater than the cost for persons aged <65 years, and the rapid growth in the number of older persons, coupled with continued advances in medical technology, is expected to create upward pressure on health- and long-term--care spending (12). In 1997, the United States had the highest health-care spending per person aged >65 years ($12,100), but other developed countries also spent substantial amounts per person aged >65 years, ranging from approximately $3,600 in the United Kingdom to approximately $6,800 in Canada (13). However, the extent of spending increases will depend on other factors in addition to aging (12).

The demands associated with long-term care might pose the greatest challenge for both personal/family resources and public resources. In the United States, nursing home and home health-care expenditures doubled during 1990--2001, reaching approximately $132 billion (14); of this, public programs (i.e., Medicaid and Medicare) paid 57%, and patients or their families paid 25% (14). In addition, during 2000--2020, public financing of long-term care is projected to increase 20%--21% in the United Kingdom and the United States and 102% in Japan (15). However, these increases will be less if public health interventions decrease disability among older persons, helping them to live independently.

The projected growth in the elderly support ratio (i.e., the number of persons aged >65 years per 100 persons aged 20--64 years) also is a concern (2). If the number of working taxpayers relative to the number of older persons declines, inadequate public resources and fewer adults will be available to provide informal care to older, less able family members and friends. However, the ratio does not account for potential increases in the numbers of persons aged >65 years who continue to work and/or care for themselves.

Reported by: MR Goulding, PhD, Div of Health and Utilization Analysis, National Center for Health Statistics; ME Rogers, MPH, SM Smith, MD, Div of Adult and Community Health, National Center for Chronic Disease Prevention and Health Promotion, CDC.

Editorial Note:

The anticipated increase in the number of older persons will have dramatic consequences for public health, the health-care financing and delivery systems, informal caregiving, and pension systems. Although more attention has been given to population aging projections and their implications in developed countries, greater numbers of older adults and increasing chronic disease will place further strain on resources in countries where basic public health concerns (e.g., control of infectious diseases and maternal and child health) are yet to be addressed fully.

To address the challenges posed by an aging population, public health agencies and community organizations worldwide should continue expanding their traditional scope from infectious diseases and maternal/child health to include health promotion in older adults, prevention of disability, maintenance of capacity in those with frailties and disabilities, and enhancement of quality of life. Because behaviors that place persons at risk for disease often originate early in life, the public health system should support healthy behaviors throughout a person's lifetime (16). Public health also should develop and support better methods and systems to monitor additional health outcomes that are related to older adults, such as functioning and quality of life.

CDC's Advisory Committee to the Director has identified five roles for CDC to promote health and prevent disease in older adults: 1) to provide high-quality health information and resources to public health professionals, consumers, health-care providers, and aging experts; 2) to support health-care providers and health-care organizations in prevention efforts; 3) to integrate public health prevention expertise with the aging services network; 4) to identify and implement effective prevention efforts; and 5) to monitor changes in the health of older adults. These roles will require new efforts to address the special needs of older adults and to deliver programs in communities in which older adults work, reside, and congregate. Existing public health programs will be required to examine whether they meet the needs of an aging population.


  1. United Nations. Report of the Second World Assembly on Aging. Madrid, Spain: United Nations, April 8--12, 2002.
  2. Kinsella K, Velkoff V. U.S. Census Bureau. An Aging World: 2001. Washington, DC: U.S. Government Printing Office, 2001; series P95/01-1.
  3. U.S. Census Bureau. International database. Table 094. Midyear population, by age and sex. Available at
  4. U.S. Census Bureau. State and national population projections. Available at
  5. Campbell PR. Population projections for states by age, sex, race, and Hispanic origin: 1995 to 2025. U.S. Bureau of the Census, Population Division, PPL-47, 1996. Available at
  6. World Health Organization. World Health Report 2002, Annex Table 2 (deaths by cause, sex and mortality stratum in WHO Regions, estimates for 2001). Geneva, Switzerland: World Health Organization, 2002:186--91.
  7. National Center for Chronic Disease Prevention and Health Promotion, CDC. Chronic disease notes and reports: special focus. Healthy Aging 1999;12:3.
  8. Boyle JP, Honeycutt AA, Narayan KMV, et al. Projection of diabetes burden through 2050: impact of changing demography and disease prevalence in the US. Diabetes Care 2001;24:1936--40.
  9. CDC. Prevalence of self-reported arthritis or chronic joint symptoms among adults---United States, 2001. MMWR 2002;51:948--50.
  10. Hubert H, Bloch D, Oehlert J, Fries J. Lifestyle habits and compression of morbidity. Journal of Gerontology: Medical Sciences 2002;57A:347--51.
  11. Freedman VA, Martin LG, Schoeni RF. Recent trends in disability and functioning among older adults in the United States: a systematic review. JAMA 2002;288:3137--46.
  12. Jacobzone S, Oxley H. Ageing and Health Care Costs. Internationale Politik und Gesellschaft Online (International Politics and Society) 1/2002. Available at
  13. Anderson GF, Hussey PS. Population aging: a comparison among industrialized countries. Health Affairs 2000;19:191--203.
  14. Levit K, Smith C, Cowan C, Lazenby H, Sensenig A, Catlin A. Trends in U.S. health care spending, 2001. Health Affairs 2003;22:154--64.
  15. Jacobzone S. Coping with aging: international challenges. Health Affairs 2000;19:213--25.
  16. Koplan JP, Fleming DW. Current and future public health challenges. JAMA 2000;284:1696--8.

* The "developing" and "developed" country categories used in this report correspond directly to the "less developed" and "more developed" classification employed by the United Nations. Developed countries comprise all nations in Europe and North America, and Japan, Australia, and New Zealand. The remaining nations are classified as developing countries. Although these categories are used commonly for comparative purposes, they no longer accurately reflect developmental differences among countries (2).


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