Temporal trends and disparities of population attributable fractions of modi fi able risk factors for dementia in China: a time-series study of the China health and retirement longitudinal study (2011 - 2018)

Background In China, dementia poses a signi fi cant public health challenge, exacerbated by an ageing population and lifestyle changes. This study assesses the temporal trends and disparities in the population-attributable fractions (PAFs) of modi fi able risk factors (MRFs) for new-onset dementia from 2011 to 2018. Methods We used data from the China Health and Retirement Longitudinal Study (CHARLS), covering 75,214 pers on-waves. We calculated PAFs for 12 MRFs identi fi ed by the Lancet Commission (including six early-to midlife factors and six late -li fe factors). We also determined the individual weighted PAFs (IW-PAFs) for each risk factor. Subgroup analyses were conducted by sex, socio-economic status (SES), and geographic location. Findings The overall PAF for dementia MRFs had a slight increase from 45.36% in 2011 to 52.46% in 2018, yet this change wasn ' t statistically signi fi cant. During 2011 - 2018, the most contributing modi fi able risk was low education (average IW-PAF 11.3%), followed by depression, hypertension, smoking, and physical inactivity. Over the eightyear period, IW-PAFs for risk factors like low education, hypertension, hearing loss, smoking, and air pollution showed decreasing trends, while others increased, but none of these changes were statistically signi fi cant. Sexspeci fi c analysis revealed higher IW-PAFs for traumatic brain injury (TBI), social isolation, and depression in women, and for alcohol and smoking in men. The decline in IW-PAF for men ' s hearing loss were signi fi cant. Lower-income individuals had higher overall MRF PAFs, largely due to later-life factors like depression. Earlylife factors, such as TBI and low education, also contributed to SES disparities. Rural areas reported higher overall MRF PAFs, driven by factors like depression, low education, and hearing loss. The study also found that the gap in MRF PAFs across different SES groups or regions either remained constant or increased over the study period. Interpretation The study reveals a slight but non-signi fi cant increase in dementia ' s MRF PAF in China, underscoring the persistent relevance of these risk factors. The fi ndings highlight the need for targeted public health strategies, considering the demographic and regional differences, to effectively tackle and reduce dementia risk in China ' s diverse population.