Cross-national dietary systems and dementia incidence: an ecological analysis of gluten-containing cereal protein supply

Background: Dietary patterns vary widely across countries and reflect broader food systems and socioeconomic development. Ecological associations between diet and dementia may therefore capture structural alignment rather than etiologically relevant exposure. This study examined cross-national associations between gluten-containing cereal protein supply derived from wheat, barley, rye, and oats and Alzheimer’s disease and other dementias (ADOD) incidence across 204 countries. Methods: Cross-national datasets were analysed using Pearson’s and Spearman’s correlations to assess associations between per-capita gluten-containing cereal protein supply from FAO food balance sheets and ADOD incidence estimates from the Global Burden of Disease study. Partial correlations adjusted for population ageing, economic affluence, and urbanisation. Principal component analysis examined shared variance among predictors, and multiple linear regression models assessed relative contributions. Results: Globally, ADOD incidence was strongly aligned with population ageing and economic development. Gluten-containing cereal protein supply showed modest ecological correlations with ADOD incidence, with heterogeneity across regions. Positive associations were observed mainly in developing settings, whereas associations were attenuated, inverse, or non-significant in developed contexts. After adjustment, the association weakened, accounting for approximately two to three percent of residual variance. Regression analyses identified population ageing and economic affluence as dominant correlates, while gluten-containing cereal protein supply contributed marginally. Principal component analysis revealed a dominant component explaining sixty percent of shared variance. Conclusion: Cross-national variation in ADOD incidence is driven primarily by demographic ageing and socioeconomic development. Gluten-containing cereal protein supply functions as a contextual marker of dietary systems rather than an independent contributor. These findings are exploratory and hypothesis-generating.