Findings indicate a substantial genetic effect for these predominantly late-onset Alzheimer's disease cases. At the same time, structural modeling results and large intra-pair differences in age of onset suggest that environmental factors are also important in determining whether and when an individual may develop dementia.
Introduction
Rapid growth of the older adult population requires greater epidemiologic characterization of dementia. We developed national prevalence estimates of diagnosed dementia and subtypes in the highest-risk U.S. population.
Methods
We analyzed CMS administrative enrollment and claims data for 100% of Medicare fee-for-service beneficiaries enrolled during 2011-2013, and age > 68 years as of December 31, 2013 (n = 21.6 million).
Results
Over 3.1 million (14.4%) beneficiaries had a claim for a service/treatment for any dementia subtype. Dementia not otherwise specified was the most common diagnosis (present in 92.9%). The most common subtype was Alzheimer's (43.5%), followed by vascular (14.5%), Lewy body (5.4%), frontotemporal (1.0%), and alcohol induced (0.7%). The prevalence of other types of diagnosed dementia was 0.2%.
Discussion
This study is the first to document concurrent prevalence of primary dementia subtypes among this U.S. population. The findings can assist in prioritizing dementia research, clinical services, and caregiving resources.
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