Prevalence of dementia in Chamorros on Guam

Objectives: To estimate the prevalence of dementia and its clinical subtypes among Chamorros on Guam aged 65 years or older and to examine associations with age, gender, education, and APOE genotype. Background: Chamorros, the indigenous people of Guam, had a high incidence of ALS and parkinsonism–dementia complex (PDC), in the 1950s. Over the next 50 years, ALS incidence declined markedly, but PDC only slightly. The prevalence of late life dementia in Chamorros and its relationship to ALS/PDC are unknown. Methods: Island-wide population-based survey of Chamorros aged 65 years or older as of January 1, 2003. Two-stage assessment: cognitive and motor screening, followed by neurologic and psychometric evaluation. Data were reviewed at consensus conference to make clinical diagnoses. Results: Of 2,789 Chamorros aged 65 years or older, 73% were enrolled; 27% declined participation, died before contact or screening, or moved off Guam. The point prevalence of all-cause dementia on February 1, 2004, was 12.2%. Prevalence data for subtypes were as follows: Guam dementia (clinically equivalent to AD), 8.8%; PDC, 1.5%; pure vascular dementia, 1.3%; other, 0.6%. The prevalence of dementia rose exponentially with age. Low education was significantly associated with dementia, but gender was not. There was a trend toward higher PDC prevalence among men. The APOE ε4 allele was not associated with dementia. Conclusions: The prevalence of dementia among elderly Chamorros is relatively high. Guam dementia is the most common diagnosis and exceeds parkinsonism–dementia complex. Age and low education are strongly associated with dementia, but gender and APOE ε4 are not. Incidence studies will allow risk factors for dementia to be clarified.