Dementia incidence across countries: a sex-specific ecological analysis of cancer incidence.

BACKGROUND

Dementia incidence is rising globally with population aging and improved survival from chronic diseases. Cancer incidence may reflect longevity, diagnostic capacity, socioeconomic development, and demographic transition, but sex-specific population-level evidence on its association with dementia incidence remains limited.

METHODS

Country-level associations between cancer incidence in 2019 and dementia incidence in 2023 were examined separately for females and males across 204 countries. Analyses included bivariate correlations, principal component analysis, partial correlations, and forced-entry regression models adjusted for gross domestic product per capita adjusted for purchasing power parity, urbanization, reduced selection opportunity, and sex-specific life expectancy at age 60.

RESULTS

Cancer incidence was positively associated with dementia incidence in both sexes. Globally, cancer incidence correlated strongly with dementia incidence among females (r = 0.765, p < 0.001) and males (r = 0.781, p < 0.001). In adjusted models, cancer incidence remained associated with dementia incidence in females (β = 0.496, p < 0.001; adjusted R2 = 0.693) and males (β = 0.526, p < 0.001; adjusted R2 = 0.709). Incremental explained variance was larger among males.

CONCLUSIONS

Cancer incidence is a sex-specific country-level correlate of dementia incidence. Findings indicate population-level co-variation, not individual-level risk or causality in aging populations worldwide.