Survey of the incidence of elderly dementia of Kazak ethnic group in Xinjiang Uygur Autonomous Region

Abstract

Objective To investigate the morbidity and epidemiology of dementia in old people and Alzheimer’s disease (AD) in Kazak and Han ethnic groups in Xinjiang Uygur Autonomous Region. Methods Using stratified cluster random sampling method, we conducted this survey within 3 663 subjects randomly selected from the residences (≥55 years old) including Kazak and Han ethnic groups in Aletai area, northern Xinjiang. The diagnosis of dementia was confirmed by the American Diagnostic and Statistical Manual of Mental Disorders (DSM-Ⅳ) based on two-stage investigation including screening and confirmed diagnosis. The diagnostic criteria of AD was according to the reference standards of the American Institute of Neurology, the Language Barrier and Stroke and the AD and Related Disorders Association (NINCDS-ADRDA). The diagnostic criteria of vascular dementia (VaD) was based on American National Institute of Neurological Disorders and Stroke Research Institute and the Swiss Neuroscience Research International Association (NINDS/AIREN). Results (1) The crude prevalence rates of AD in Kazak and Han ethnic groups were 5.88% (149/2 532) and 4.45%（48/1 078）, respectively and the age-adjusted rates were 5.64% and 4.73%, respectively. These two rates of VaD in Kazak and Han ethnic groups were 2.69% (68/2 532) and 1.95% (21/1 078), 2.43% and 1.99%, respectively. There were no significant differences between two ethnic groups. (2) The AD morbidity in female and male was 7.32% (96/1 311) and 4.34% (53/1 221;χ2=15.807, P<0.01) respectively in Kazak population; While it was 6.02%(35/581) and 2.62% (13/497;χ2=12.571, P<0.01) in Hans. The morbidity difference was statistically significant in different educational levels. However， there was no statistically significant difference in subjects with same degree of education. In VaD, there was no correlation between educational level and morbidity in both Kazak and Han people. (3) The morbidity of dementia was sharply increased with age in two populations, especially in patients over 80 years old with the highest of 30.28% (66/218). Conclusions AD is the main type of dementia in old Kazak and Han people in Xinjiang, while VaD is the second reason of dementia. The morbidity rate of AD in female is significantly higher than men in both two ethnic groups. The lower level of education is associated with the higher incidence of AD and the morbidity of AD and VaD is increased with age. Key words: Alzheimer disease; Dementia, vascular; Prevalence; Sampling studies