Subjective Cognitive Decline in Brazilian Adults: Prevalence and Associated Social, Lifestyle, and Health-Related Factors: A Nationally Representative Cross-Sectional Analysis from the ELSI-Brazil Cohort

Background/Objectives: Subjective cognitive decline (SCD) is an early stage of dementia, although its risk factors remain unclear. We estimated the prevalence of SCD and its associated dementia risk factors in Brazilian adults. Methods: This cross-sectional study is based on data from the second wave (2019–2021) of the Brazilian longitudinal study of aging (ELSI-Brazil) and a nationally representative sample of adults aged ≥50 years. Prevalence of SCD was estimated and defined as self-reported cognitive decline without objective impairment or dementia diagnosis, and the adjusted odds ratios (OR) with 95% confidence intervals (CI) were estimated through logistic regression models. Results: Of 6631 participants, 57.5% were women, and 54.4% were non-white, with a mean age of 65.1 years (standard deviation: ±9.70). SCD prevalence was 19.7% (95% CI 18.6–20.9) for a total of 1346 individuals. Significantly strong positive associations with SCD were observed for sociodemographic factors, particularly lower education (OR = 2.79, 95% CI: 2.02–3.85), as well as older age, non-white ethnicity, and lower income (ORs ranging from 1.50 to 1.79). Lifestyle factors, including loneliness and sedentary behavior, showed moderate associations (OR = 1.33 and 1.35, respectively). Among health-related conditions, multimorbidity was significantly associated with higher odds of SCD (OR = 1.40 for ≥3 chronic diseases), with the strongest association observed for hearing loss (OR = 2.29, 95% CI: 1.93–2.71). Diabetes, visual loss, and depressive symptoms showed more modest significant associations (OR 1.25 to 1.31). Conclusions: Our findings support the prioritization of vulnerable populations in public health strategies aimed at promoting healthy ageing and reducing social and health inequalities. Longitudinal studies are needed to clarify whether modifying associated factors may influence SCD trajectories.