As Many as 47 Million Americans May Have Preclinical Alzheimer’s Disease
Prevention Strategies
The team remodeled those numbers in three hypothetical intervention scenarios. Researchers say that a treatment that slows decline by at least 30% would have a meaningful clinical, financial, and societal impact. However, Dr. Brookmeyer modeled treatment scenarios with a greater effect.
A primary prevention method that reduced the annual risk of new amyloidosis by 50% could decrease the prevalence of MCI by about 700,000 in 2060. A secondary prevention strategy that reduced the annual risk progression to MCI by 50% would decrease the prevalence of MCI by more than two million and the prevalence of Alzheimer’s disease by about 3.8 million.
The results were more complicated with a secondary prevention strategy that would reduce annual risk of conversion from MCI to Alzheimer’s disease by 50%. In this scenario, the prevalence of MCI in 2060 would increase by 2.8 million, but the prevalence of Alzheimer’s disease would decrease by 2.5 million. These scenarios developed over different time courses, said the researchers.
“We find that the highly effective primary prevention strategy resulted in the lowest Alzheimer’s disease prevalence by the year 2060. However, [it] was associated with the largest Alzheimer’s disease prevalence in the 15 years immediately after its introduction ... The explanation for this finding is that the full benefits of delaying amyloidosis, in terms of reduced Alzheimer’s disease prevalence, are not realized for many years because of the long lag time between amyloidosis and clinical Alzheimer’s disease. A take-home message is that the full impact on disease burden of primary prevention that targets the early stages of the pathogenesis of Alzheimer’s disease may not be realized for decades.”
Decreasing preclinical conversion to MCI with a secondary prevention strategy would result in the highest Alzheimer’s disease prevalence reduction for most of the period. But the reduction resulting from the primary prevention strategy would surpass it by 2054.
The intervention targeting conversion from MCI to Alzheimer’s disease would reduce Alzheimer’s disease prevalence the quickest, with a slight decrease in the first three years after introduction. “The explanation for this finding is that MCI is proximate to clinical Alzheimer’s disease diagnosis, and thus the impact of delaying progression of MCI will be seen relatively quickly on Alzheimer’s disease prevalence, compared to interventions that delay onset of amyloidosis or MCI.
“By focusing attention on a concerning reality—that tens of millions of American adults may face the possibility of dementia due to Alzheimer’s disease—the results reported in this new article, if confirmed, illustrate and greatly amplify the need for more research to develop effective treatments and proven prevention strategies for Alzheimer’s disease,” said Dr. Brookmeyer. “This is especially true as we get better at early detection and are able to more accurately identify people who have the early brain changes associated with Alzheimer’s disease and other dementias.”
Dr. Brookmeyer reported receiving fees from Takeda for serving as a member of a data safety monitoring board.
—Michele G. Sullivan
Suggested Reading
Brookmeyer R, Abdalla N, Kawas CH, Corrada MM. Forecasting the prevalence of preclinical and clinical Alzheimer’s disease in the United States. Alzheimers Dement. 2017 Nov 29 [Epub ahead of print].
Derby CA, Katz MJ, Lipton RB, Hall CB. Trends in dementia incidence in a birth cohort analysis of the Einstein Aging Study. JAMA Neurol. 2017;74(11):1345-1351.
Sperling RA, Aisen PS, Beckett LA, et al. Toward defining the preclinical stages of Alzheimer’s disease: recommendations from the National Institute on Aging-Alzheimer’s Association workgroups on diagnostic guidelines for Alzheimer’s disease. Alzheimers Dement. 2011;7(3):280-292.
Vos SJ, Verhey F, Frölich L, et al. Prevalence and prognosis of Alzheimer’s disease at the mild cognitive impairment stage. Brain. 2015;138(Pt 5):1327-1338.
