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Using new methodology, scientists calculate that approximately 6 million American adults have Alzheimer's disease or mild cognitive impairment, which can sometimes be a precursor to the disease. The estimate, funded by the National Institutes of Health, also forecasts that these numbers will more than double to 15 million by 2060, as the population ages.

The estimates are published online Dec. 7, 2017, in the journal Alzheimer's & Dementia: the Journal of the Alzheimer's Association.

This new forecast differs from earlier estimates. For the first time, have attempted to account for numbers of people with biomarkers or other evidence of possible preclinical Alzheimer's disease, but who do not have impairment or Alzheimer's . People with such signs of preclinical disease are at increased risk to develop Alzheimer's dementia.

The researchers say they factored those rates of transition in their multi-state model; further, the model can estimate the impact of some possible prevention efforts on the number of future cases.

More information: Ron Brookmeyer et al. Forecasting the prevalence of preclinical and clinical Alzheimer's disease in the United States, Alzheimer's & Dementia (2017). DOI: 10.1016/j.jalz.2017.10.009