INCIDENCE AND SUBTYPES OF DEMENTIA IN SOUTHERN TAIWAN - IMPACT OF SOCIODEMOGRAPHIC FACTORS

Objective: To determine the incidence rate (IR) and subtypes of dement ia in southern Taiwan. Methods: From a cohort of 2,915 community inhab itants aged 65 years and over, 2,507 and 2,175 subjects participated i n the first-and second-year follow-up surveys, respectively. A tare-ph ase study used the Mini-Mental State Examination in phase I and the Co nsortium to Establish a Registry of Alzheimer's Disease (CERAD) neurop sychological battery and the neurobehavioral examination in phase II. We applied International Classification of Diseases (ICD)-10NA criteri a for dementia, National Institute of Neurological and Communication D isorders and Stroke-Alzheimer's Disease and Related Disorders Associat ion (NINCDS-ADRDA) guidelines for Alzheimer's disease (AD), and Nation al Institute of Neurological Disorders and Stroke-Association Internat ionale pour la Recherche et l'Enseignement en Neurosciences (NINDS-AIR EN) criteria for vascular dementia (VaD). Results: The annual IR for t otal dementia was 1.28%, which increased with age from 0.77% for 65- t o 74-year-olds to 6.19% for persons aged 85 years or older. AD (25 cas es, 41.7%, IR = 0.54%) was the most common cause of dementia, followed by VaD (19 cases, 31.7%, IR = 0.41%) and mixed dementia (9 cases, 15. 0%). After adjusting for sex, increasing age was significantly associa ted with total dementia and AD (p < 0.01). Illiteracy was associated w ith a marginally increased risk for total dementia (aRR = 1.59, p < 0. 1) as was being female for AD (aRR = 1.92, p < 0.1). The a-year mortal ity rate was high among the demented (48% in total dementia, 38% in AD , and 60% in VaD). Conclusions: The age-specific incidence of dementia in Taiwan is approaching that of developed countries and the low prev alence of dementia (especially VaD) may be mainly due to the high mort ality. Age was the major risk factor for total dementia and AD. Being female was probably a risk factor for AD, as was illiteracy for total dementia.