Abstract
The goal of this study was to project the future prevalence and incidence of Alzheimer's disease in the United States and the potential impact of interventions to delay disease onset. The numbers of individuals in the United States with Alzheimer's disease and the numbers of newly diagnosed cases that can be expected over the next 50 years were estimated from a model that used age-specific incidence rates summarized from several epidemiological studies, US mortality rates, and US Bureau of the Census projections. in 1997, the prevalence of Alzheimer's disease in the United States was 2.32 million (range: 1.09 to 4.58 million); of these individuals, 68% were female. It is projected that the prevalence will nearly quadruple in the next 50 years, by which time approximately 1 in 45 Americans will be afflicted with the disease. Currently, the annual number of new incident cases in 360,000. If interventions could delay onset of the disease by 2 years, after 50 years there would be nearly 2 million fewer cases than projected; if onset could be delayed by 1 year, there would be nearly 800,000 fewer prevalent cases. As the US population ages, Alzheimer's disease will become an enormous public health problem. interventions that could delay disease onset even modestly would have a major public health impact.
Highlights
E-4 allele on chromosome 19 is associated with a higher risk for late-onset Alzheimer's disease.' Several putative factors have recently been suggested that may delay the onset of Alzheimer's disease, including the use of anti-inflammatory drugs, nonsteroidals,2>6 and estrogen replacement therapy in women.]-12 While confirmation of these preliminary findings must await larger epidemiological studies and randomized prevention trials, they suggest avenues for future prevention programs that may have a significant public health impact
In reviewing studies reporting such rates, we initially considered only studies of US populations because of concerns regarding cross-cultural differences'-'5; as discussed later, our results are very consistent with those of a number of intemational studies, of European populations.'[6] Four studies of US populations that reported age-specific incidence rates were identified; these studies were conducted in Framingham, Mass'[7]; East Boston, Massl[8]; Rochester, Minn'[9]; and Baltimore, Md.[20]
Even a modest 6-month delay would correspond to an annual savings of perhaps $4.7 billion at 10 years after initiation of the intervention and nearly $18 billion annually after 50 years. Caveats associated with these estimates are that they were based on annual costs of $47 000 and were derived from a single study conducted in the San Francisco Bay area that may not have accurately reflected costs in other parts ofthe country. These analyses suggest that the number of Americans with Alzheimer's disease in 1997 was 2.32 million and that this number will nearly quadruple in the 50 years, at which time 1 in 45 Americans will be living with the disease
Summary
E-4 allele on chromosome 19 is associated with a higher risk for late-onset Alzheimer's disease.' Several putative factors have recently been suggested that may delay the onset of Alzheimer's disease, including the use of anti-inflammatory drugs, nonsteroidals,2>6 and estrogen replacement therapy in women.]-12 While confirmation of these preliminary findings must await larger epidemiological studies and randomized prevention trials, they suggest avenues for future prevention programs that may have a significant public health impact. Estimates of the future incidence and prevalence of Alzheimer's disease are important for projecting future institutional and home health care needs and the economic burden of this disease. There are uncertainties in estimates of the numbers of individuals living with Alzheimer's disease. This uncertainty arises because of methodological differences among the limited number of epidemiological studies that have directly measured incidence and prevalence rates in community-based populations and because of the difficulty in establishing a precise age of onset of a disease that follows a gradually progressive, insidious course. The objectives of this article are to estimate the future incidence and prevalence of Alzheimer's disease and to quantify the potential impact on these estimates of interventions that could delay the onset ofdisease
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