Résumé
Background
In animal models, carbohydrates increase β‐amyloid aggregation, tau phosphorylation and hippocampal atrophy which lead to the development of Alzheimer’s disease (AD). In epidemiological studies, cross‐sectional analyses on the impact of carbohydrate consumption on cognition are inconsistent. Besides, the long‐term effects of high carbohydrate intake on the risk of dementia and AD are poorly described. Here, we investigated i) the association between glycaemic load (GL) and cognition ii) the longitudinal association between GL and the onset of dementias (AD and others dementias) and iii) the associations between GL and plasma β‐amyloid peptides (Aβ) (possible biomarkers of AD pathology).
Method
No less than 2,777 non‐demented participants from the Three‐City Study (Bordeaux and Montpellier centre), aged over 65, filled a complete semi‐quantitative Food Frequency Questionnaire which was used to estimate GL (GL assesses both the carbohydrate quantity and quality, and reflects glycaemic response). At baseline, participants underwent a battery of neuropsychological tests (global cognition, visual memory, executive function, verbal fluency). Clinical diagnosis of dementia was made at each follow‐up (every 2‐3 years during 12 years). In a sub‐sample of 378 participants, plasma Aβ was measured. Plasma levels of Aβ1–40, Aβ1–42, Aβn‐40, and Aβn‐42 were measured using an xMAP‐based assay technology. We used Cox proportional hazards models to test the association between GL and the onset of dementia and linear regressions to test the associations between GL and cognitive performance or plasma Aβ.
Result
After adjustment for potential confounders (age, sex, education, APOE‐ε4, BMI, type 2 diabetes, hypertension, cardiovascular history, history of stroke, hypercholesterolemia, history of head trauma, good subjective health, tobacco, energy intake, Mediterranean diet, physical activity), high afternoon‐snack GL was associated with increased dementia risk in APOE‐ε4 carriers (HR = 1.27 [1.03‐1.56]). Unexpectedly, GL was associated with higher cognitive performance, particularly for global cognition and visual memory (p <.01). We found no significant association between GL and plasma Aβ.
Conclusion
High carbohydrate consumption was associated with a long‐term risk of dementia in APOE‐ε4 carriers. However, carbohydrate consumption seems to promote short‐term cognitive performance.