Global Correlation Between Cancer Incidence and Dementia Incidence Based on Cross National Regression Analyses

Background: Cancer and dementia are two major global health challenges shaped by population ageing and socioeconomic transitions. Both impose substantial burdens, yet their interrelationship at the population level remains underexplored. This study examined the global relationship between cancer incidence and dementia incidence, taking into account developmental, demographic, and healthcare-related covariates. Methods: Data on cancer incidence and dementia incidence were obtained from the Institute for Health Metrics and Evaluation. Covariates included economic affluence, urbanisation, selection opportunity, and life expectancy at age 60. Analyses across 204 countries employed Pearson and Spearman correlations, partial correlations, principal component analysis, and multiple linear regression (enter and stepwise). Subgroup analyses were stratified by World Bank income level, UN development status, WHO regions, and additional geopolitical groupings. Results: Cancer incidence was strongly correlated with dementia incidence globally (r = 0.873; ρ = 0.938, p < 0.001). Associations remained robust across regions and income groups, particularly in upper-middle-income and developing countries. Partial correlations confirmed the relationship persisted after adjusting for covariates, with cancer explaining 59.8% of dementia variance. In regression models, socioeconomic and demographic factors explained 51.7% of variance; adding cancer increased explanatory power to 80.1%. Cancer uniquely accounted for 28.3% in the enter model and 28.8% in the stepwise model, confirming its role as the dominant independent predictor. Conclusion: Cancer incidence is strongly and independently associated with dementia incidence worldwide, surpassing traditional predictors. Findings highlight shared determinants and underscore the importance of integrated chronic disease strategies, particularly in low-resource settings.