Supplementary Material for: Ageing, Wealth, and Diet: A Global Cross-National Analysis of Cereal Consumption and Dementia Risk

Background:
Global variation in dementia incidence reflects demographic and socioeconomic forces, yet the role of staple dietary patterns remains less defined. While population ageing is a key determinant of dementia burden, differences in cereal consumption, particularly rice, wheat, and maize, have received limited attention. This ecological study examined whether national cereal consumption patterns are associated with dementia incidence across countries independent of confounding factors.
Methods:
Country level data from 204 nations were compiled, with complete case analyses conducted in 184 countries. Alzheimer’s disease and other dementias incidence in 2021 served as the outcome variable. Predictors included per capita consumptions of total cereals, rice, wheat, and maize, alongside genetic predisposition, economic affluence, urban living, ageing indexed by life expectancy at age sixty, and meat consumption. Pearson and partial correlations, principal component analysis, and stepwise multiple regression were applied.
Results:
Wheat consumption was positively associated with dementia incidence, affluence, and longevity, whereas rice and maize consumption showed inverse associations. Partial correlations confirmed a persistent inverse association for rice consumption and a weaker inverse association for total cereal consumption after adjustment. Principal component analysis identified a socioeconomic component aligned with wheat consumption and ageing, while rice and maize loaded inversely. Stepwise regression demonstrated that ageing was the strongest predictor of dementia incidence, while rice and total cereal consumption retained small independent inverse associations.
Conclusions:
Global dementia incidence is driven primarily by population ageing and socioeconomic development. Cereal type reflects distinct developmental contexts, with rice-based patterns associated with a modestly lower dementia burden.