Population attributable fractions of modifiable dementia risk factors for cognitive impairment-the ELSA-Brasil cohort study.

Background: Population attributable fractions (PAF) of modifiable dementia risk factors are rarely estimated in low- and middle-income countries. We aim to estimate the relative risk (RR) for cognitive impairment and calculate the PAF in the (ELSA-Brasil).

Methods: We analyzed adults aged 35-74 at the baseline (2008-2010) and wave 3 (2017-2019). We estimated the prevalence of eight modifiable dementia risk factors at baseline: hypertension, physical inactivity, diabetes, depression, obesity, low education, smoking, and excessive alcohol consumption. Cognition was evaluated at baseline and wave 3 using six standardized tests for the Brazilian Portuguese. A global cognitive score from the individual cognitive tests was created using calculated z-scores each test. A global z-score below -1.5 was considered indicative of cognitive impairment. We calculated the RR and PAF for cognitive impairment at wave 3.

Findings: We followed 10,058 adults (56.7% women, median age of 50 [IQR: 44-56] years) for 8.1 (0.6) years. The eight-year incidence of cognitive impairment in wave 3 was 5.5% (n = 549). Low education had the largest RR (4.32) followed by hypertension (1.43), diabetes (1.27), and smoking (1.35). Low education had the largest PAF (95% CI), 14.2% (11.2-17.3), followed by hypertension 13% (7-19), diabetes 4.2% (0.7-7.7), and smoking 3.2% (0.45-6). The total PAF for significant risk factors was 34.7% (28.2-41.3).

Interpretation: The findings highlight the importance of early-life and midlife prevention strategies in low- and middle-income countries, with a focus on addressing educational and cardiovascular risk factors.

Funding: RMC received Alzheimer's Association grant (AARGD-21-846545).