Prevalence and progression of subjective cognitive decline among rural Chinese older adults: A Population‐based follow‐up study

Abstract Background Few studies have examined occurrence and progression of subjective cognitive decline (SCD) in rural China. We aimed to investigate the prevalence of SCD and explore factors associated with progression from SCD to cognitive impairment, no dementia (CIND) and Alzheimer’s disease (AD). Method This community‐based study included 2488 cognitively unimpaired participants (age ≥65 years; 55.18% women; and 39.87% illiterate) in the Shandong Yanggu Study of Aging and Dementia who were examined at baseline (2014‐2015), of these, 1843 were followed in 2018. Demographic, epidemiological, clinical, and neuropsychological data were collected following a structured questionnaire. SCD was defined based on the Chinese version of the self‐rated Ascertain Dementia 8‐item Questionnaire (AD8) score. CIND and AD were diagnosed following the international criteria. Data were analyzed with the multivariate logistic regression models. Result At baseline, 997 of the 2488 participants were defined to have SCD. The prevalence of SCD was 40.07%, and the prevalence was increased with age. Of the 1843 participants in the follow‐up examination in 2018, 189 were diagnosed with CIND and 58 with AD. Having SCD at baseline was significantly associated with the multi‐adjusted odds ratio (OR) of 1.55 (95% confidence interval = 1.14‐2.12) for incident CIND and 2.91 (1.56‐5.42) for incident AD. Of 745 participants with SCD at baseline, 97 progressed to CIND and 43 to AD during the average 3.79 years of follow‐up. Multivariable logistic regressions showed that the multi‐adjusted OR of incident CIND was 0.51 (0.26‐0.98) for high social support, whereas the multi‐adjusted OR of incident AD was 1.22 (1.14‐1.31) for older age (per 1‐year increment), 0.31 (0.11‐0.85) for high education, 2.77 (1.17‐6.57) for carrying the apolipoprotein E (APOE) ε4 allele, 0.29 (0.11‐0.75) for high social support, and 3.98 (1.37‐11.52) for mild depressive symptoms. Conclusion SCD affects over 40% of rural‐dwelling older adults in China who are free of cognitive impairment. Older people with SCD are more likely to develop CIND and AD. Older age, illiteracy, APOE ε4 allele, low social support, and depressive symptoms are associated with accelerated progression from SCD to CIND or AD.