Abstract INTRODUCTION: In animal models, refined carbohydrates (RF) worsen Alzheimer’s disease (AD). However, the long-term effects of high RF intake on the risk of dementia and AD are poorly described in epidemiological studies. Moreover, the interaction between RF and apolipoprotein E ε4 allele (APOE-ε4) is unknown. Our study investigated whether RF-rich diets are associated with the risk of dementia and AD. METHODS: The glycemic load was quantified in 2,777 elderly participants from the French Three-City Study to estimate RF intake. Then, the association between glycemic load and risk of dementia and AD, and the interaction with APOE-ε4 over a 12-year period were assessed using proportional hazards models. RESULTS: After adjustment for potential confounders, high afternoon-snack glycemic load was associated with increased dementia and AD risk in APOE-ε4 carriers (HR = 1.27 [1.03-1.56]). DISCUSSION: This study highlights that RF-rich diets are a risk factor for dementia and AD in APOE-ε4 carriers.