Cancer and dementia incidence are strongly correlated worldwide: evidence from cross-national regression analyses

Background: Cancer and dementia are two major global health challenges influenced by population aging and socioeconomic transitions. Both impose substantial burdens, yet their relationship at the population level is insufficiently explored. This study investigated the global association between cancer incidence and dementia incidence, while accounting for developmental, demographic, and healthcare-related factors. Methods: Data were obtained from the Institute for Health Metrics and Evaluation. Covariates included economic affluence, urbanization, reduced selection opportunity, and life expectancy e(60). Analyses across 204 countries employed correlations, partial correlations, principal component analysis, and multiple linear regression (enter and stepwise). Subgroup analyses were stratified by income level, development status, WHO regions, and geopolitical groupings. Results: Cancer incidence was strongly correlated with dementia incidence worldwide (r = 0.873; ρ = 0.938, p < 0.001). Associations remained consistent across regions, particularly in upper-middle-income and developing countries. Partial correlations showed the relationship persisted after adjustment, with cancer explaining 59.8% of dementia variance. Regression models revealed that socioeconomic and demographic factors explained 51.7% of the variance, rising to 80.1% with cancer included. Conclusion: Cancer incidence is a dominant independent predictor of dementia incidence globally, surpassing traditional factors. Findings highlight shared determinants and emphasize the importance of integrated chronic disease strategies, especially in low-resource settings.