Estimated Number of People With AD

The results of our meta-analysis, based on the pooling of the data of individuals from each of the studies, were used to project the numbers of Americans, in 1995, with (1) AD of any level of severity (mild, moderate, or severe) and (2) moderate or severe AD (see table 1). The AD prevalence estimates are generated by multiplying prevalence rates (discussed in the section below called “Estimated Prevalence Rates”) by the corresponding age- and gender-specific 1995 estimates from the Bureau of the Census.When these results are summed over the several age intervals and both genders, the overall estimate for Americans 65 years of age or older with any AD is 1.9 million. When adjusted for the cases of mixed dementia and missed cases not included in some of the studies, these percentages become 6.3 and 4.1, respectively. Projections for Numbers of People With AD

We also developed projections into the next century of the number of AD cases and the number of AD cases requiring assistance. These rates are each increased by 10 percent when all mixed cases and missed cases are included. These results demonstrate that the AD prevalence rate increases sharply with age, doubling about every 5 years at least until about the age of 85, as expected from previous reports of this relationship. In addition, the rate is greater for women than for men. NIA’s Ongoing Studies

NIA is currently supporting a number of studies of AD prevalence in the United States. Many of these studies include minority groups in addition to whites. The results of these studies are expected to be published within the next several years. The number of people with AD is at least 1.9 million now and can, with relatively conservative assumptions about population growth, be expected to grow to at least 2.9 million by 2015. Depending on severity, these cases will need some kind of long-term care. 2. 7. 8. “Prevalence of Alzheimer’s Disease and Other Dementing Disorders in Pamplona, Spain.” Neuroepidemiology, Vol. 11. (Relevant to study 7.) When this factor is applied to the estimates given above, the findings for 1995 are 2 million people with AD of any kind and 1.3 million cases of moderate or severe AD, rather than the 1.9 million and 1.1 million, respectively, that were originally reported. Comments From the National Institute on Aging

The following are GAO’s comments on NIA’s June 4, 1997, letter. 2. 5.
Why GAO Did This Study

Pursuant to a congressional request, GAO provided estimates of the prevalence of Alzheimer's Disease (AD) in the United States, including projections for prevalence in the near future.

What GAO Found

GAO noted that: (1) on the basis of existing studies, it is estimated that at least 1.9 million Americans 65 years of age or older suffered from any level of AD--mild, moderate, or severe--in 1995; (2) this number would be closer to 2.1 million if adjusted for the omissions, in many of these studies, of cases with mixed dementia and cases missed by the screening instruments used; (3) when only people likely to need at least some active assistance with personal care are considered, the results of GAO's meta-analysis show slightly more than 1 million people with AD over the age of 64; (4) the result would be higher--closer to 1.4 million people with AD--if all mixed cases and missed cases were included in all studies; (5) consistent with all earlier research, the results for both any AD and moderate or severe AD demonstrate that the prevalence rates increase sharply with age, doubling about every 5 years, at least until the age of 85, when the increase begins to slow; (6) also consistent with some earlier research, the estimated rates for women are higher than for men; (7) projecting the number of people with AD into the future gives some indication of the long-term care and research challenges that will face the nation as people grow older; (8) GAO's meta-analysis, when combined with Bureau of the Census projections, shows that more than 2.9 million people would have at least a mild case of AD in 2015; of these, over 1.7 million would need active assistance in personal care; (9) these figures jump to 3.2 million and 2.1 million, respectively, when mixed cases and missed cases are included; (10) given the uncertainty surrounding existing estimates of AD, a number of studies are now under way, supported by the National Institute on Aging, that should yield better prevalence estimates of African-Americans, Hispanics, and other nonwhite subpopulations; and (11) the results of these studies, expected to be published over the next several years, should improve GAO's picture of AD prevalence for the United States as a whole, as well as for the specific population segments studied.