Frequency of early and late‐onset dementias in a Japanese memory disorders clinic

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Abstract
The aim of this study was to compare the diagnostic profiles of patients with early (age n = 430), Alzheimer's disease (AD) (48.1%) was the most frequent cause of dementia, followed by AD with cerebrovascular disease (CVD) (31.4%), vascular dementia (VaD) (9.1%), dementia with Lewy bodies (DLB) (3.7%), frontotemporal lobar degeneration (FTLD) (1.6%), and others (5.8%). On the contrary, amongst early onset patients (n = 34), the most common dementia diagnosis was AD (38.2%), followed by VaD (23.5%), FTLD (14.7%), AD with CVD (5.9%), DLB (2.9%), and others (17.6%). FTLD and VaD were significantly more common in the early onset group. All patients, but one, with DLB and Parkinson's disease dementia were late‐onset. The relative frequencies of AD, VaD, and DLB in our series are consistent with epidemiologic findings in several Western countries; however, the frequency of FTLD is not consistent with the previous findings presenting high frequency in late‐onset patients in some Western countries.