P1‐094: Prevalence of dementia and dementing diseases in the old‐old population in Japan: MRI analyses of vascular lesions—The Kurihara Project

Abstract

There have been no reports on the prevalence of dementia and dementing diseases among the old-old people in Japan. Vascular contributions to Alzheimer's disease (AD) with cerebrovascular diseases (CVD), vascular dementia (VaD), and mixed dementia (MxD) have not been clarified. We targeted the selected old-old population aged 75+ years by block randomization (n = 1,252) in Kurihara (total population, 76,708), northern Japan.Analysis 1: 590 people agreed to participate (Participants 1): the prevalence of dementia and dementing diseases were analyzed by intensive evaluation including MRI. Locations of CVD were also assessed for the patients with AD with CVD, VaD, and MxD. Analysis 2: Participants 2 (n = 3,915) who applied the Long-Term Care Insurance (LTCI) was analyzed to estimate the prevalence of “dementia condition” based on the LTCI index. Written informed consent was obtained from all participants and the family. Analysis 1: 73 (12.4%) people were diagnosed with dementia (DSM-IV). The most common cause was AD with CVD, followed by AD (NINCDS-ADRDA), MxD (NINCDS-ADRDA and NINDS-AIREN), and VaD (NINDS-AIREN). The AD with CVD group had non-“strategic” CVDs, whereas the VaD group had at least cortical CVDs or subcortical “strategic” CVDs. For the MxD group, all had left subcortical “strategic” CVDs including the thalamus or caudate head. Analysis 2: Among the LTCI index, the I level of Impairment Level of Dementia was found to be a good indicator of “dementia condition,” the sensitivity/specificity being 0.88/0.88. As a whole, the estimated prevalence of dementia condition was 23.6%. There was a gender difference; an “age-related” increase in males and an “ageing-related” increase in females. The prevalence of dementia among the old-old population was higher than that reported previously. AD with CVD was the most common cause, coincided with the previous findings of 65+ years; however, the ratio of MxD was greater. Our data showed at least an importance of the left subcortical lesion for causing cognitive deterioration, resulting in the diagnosis of MxD. For the difference between an “age-related” increase and an “ageing-related” increase, we speculated that the prognosis after dementia onset was poorer in males.