Population-attributable fractions of risk factors for all-cause dementia in China rural and urban areas: a cross-sectional study

Background The prevalence of dementia in China, particularly in rural areas, is consistently increasing; however, research on population-attributable fractions (PAFs) of risk factors for dementia is scarce. Methods We conducted a cross-sectional survey, namely, the China Multicentre Dementia Survey (CMDS) in selected rural and urban areas from 2018 to 2020. We performed face-to-face interviews and neuropsychological and clinical assessments to reach a consensus on dementia diagnosis. Prevalence and weighted PAFs of eight modifiable risk factors (six classical: less childhood education, hearing impairment, depression, physical inactivity, diabetes, and social isolation, and two novels: olfactory decline and being unmarried) for all-cause dementia were estimated. Results Overall, CMDS included 17,589 respondents aged ≥ 65 years, 55.6% of whom were rural residents. The age- and sex-adjusted prevalence for all-cause dementia was 9.11% (95% CI 8.96–9.26), 5.19% (5.07–5.31), and 11.98% (11.8–12.15) in the whole, urban, and rural areas of China, respectively. Further, the overall weighted PAFs of the eight potentially modifiable risk factors were 53.72% (95% CI 52.73–54.71), 50.64% (49.4–51.89), and 56.54% (55.62–57.46) in the whole, urban, and rural areas of China, respectively. The eight risk factors’ prevalence differed between rural and urban areas. Lower childhood education (PAF: 13.92%) and physical inactivity (16.99%) were primary risk factors in rural and urban areas, respectively. Conclusions The substantial urban–rural disparities in the prevalence of dementia and its risk factors exist, suggesting the requirement of resident-specific dementia-prevention strategies.