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Introduction Approximately 45% of dementia cases are potentially modifiable; however, their population attributable fraction (PAF) may vary according to sociodeterminants and geographical regions. Thus, this descriptive, ecologic study aimed to estimate overall and individual global, regional and national PAFs due to 14 modifiable risk factors for dementia in adults.Methods Age-standardised prevalence, prevalence proportion and relative risk of risk factors for dementia were extracted for each nation from the Global Burden of Disease Study, WHO Observatory, World Bank and Lancet commission for dementia. Communalities by income group and weighted PAFs were calculated. Sociodemographic index (SDI), gross national income (GNI) and Health Access and Quality Index (HAQI) were used for correlation analysis with PAF.Results Approximately 34.03% (95% uncertainty interval (UI) 30.42% to 37.37%) of dementia cases were potentially preventable worldwide. South Asia accumulated the largest amounts of weighted overall PAFs (42.16% (95% UI 39.76% to 42.58%)) while Western Europe had the lowest amount (23.25% (95% UI 22.76% to 23.81%)). Globally, vision loss was the most important risk factor (4.04% (95% UI 2.88% to 5.09%), followed by low education (3.61% (95% UI 2.18% to 5.33%)) and inactivity (2.41% (95% UI 1.71% to 3.07%)). We identified regional and interregional patterns for alcohol, diabetes, hearing loss, inactivity, obesity, smoking and vision loss. Overall, PAF was negatively correlated with GNI (r=−0.39, p<0.0001), SDI (r=−0.39, p<0.0001) and HAQI (r=−0.37, p<0.0001). All individual risk factors except diabetes, smoking and inactivity were correlated with SDI and HAQI. Sensitivity analysis using a fixed communality evidenced changes in risk factors ranking within regions and distribution of PAFs.Conclusions One-third of dementia cases were potentially preventable worldwide, being vision loss, low education and inactivity their main contributors. Since estimates varied according to socioeconomic and regional-specific factors, tailored whole-population approaches should be prioritised.