The incidence of dementia among elderly people in Xi' an, China

OBJECTIVE: To explore the incidence of dementia among elderly people in Xi'an and its related risk factors. METHODS: Subjects that had been studied on the prevalence of dementia were follow-up, and the incidence of dementia, Alzheimer disease (AD) , and vascular dementia (VD) were counted by person-years. The clinical diagnosis on dementia,AD and VD were based upon the 3rd Edition of Diagnostic and Statistical of Manual of Mental Disorder, Revised version (DSM-III-R) and NINCDS-ADRDA criteria. RESULTS: 2197 subjects of non-dementia being identified in 1998, were re-surveyed in 2001. Out of them, 47 new cases of dementia including 37 cases of AD and 8 cases of VD were identified, with an annual incidence rates of dementia, AD and VD as 0.68%, 0.54% and 0.12% among those of 55 years and over and 0.89%, 0.69% and 0.17% in 65 years and over, respectively. Analysis from single factor logistic regression showed that age and education but not gender were closely related to the occurrence of AD. On the contrary, age, hypertension and stroke were closely related to the occurrence of VD. CONCLUSION: The incidence of dementia in the "Xi' an cohort" was similar to that being reported from other countries. AD and VD were an age-related diseases but education seemed to have had great protective effect while lack of formal education served as risk factor to AD.