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

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. 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. Cancer incidence was strongly correlated with dementia incidence worldwide (r = 0.873; <i>ρ</i> = 0.938, <i>p</i> &lt; 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. 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. Cancer and dementia are two major health problems affecting millions of people around the world. These conditions are becoming more common as people live longer and societies develop. Although cancer and dementia are usually studied separately, this study focused at whether countries with more cancer also tend to have more dementia. We collected information from 204 countries on how many people develop cancer and dementia each year, using large international databases. We also considered factors that differ between countries, such as income, how many people live in cities, and how long people live on average. We found a very strong link between cancer and dementia at the country level. Countries with higher cancer rates almost always have higher dementia rates. This pattern was seen in nearly every region of the world, especially in countries with growing economies and older populations. Even after we accounted for income, life expectancy, and other social factors, cancer remained one of the strongest predictors of dementia. These findings suggest that cancer and dementia share many of the same underlying causes, such as aging, chronic inflammation, lifestyle habits, and changes that come with economic development. Understanding these shared patterns can help countries plan for future healthcare needs. The results also show the importance of preventing chronic diseases through healthier lifestyles, better medical care, and stronger public health systems. Cancer incidence shows a very strong global correlation with dementia incidence across 204 countries.The association remains robust after adjusting for economic affluence, urbanization, relaxed selection opportunity, and life expectancy.Cancer incidence explains substantially more variance in dementia incidence than traditional socioeconomic and demographic factors.The cancer–dementia relationship is consistent across most income groups and world regions, especially in upper-middle-income and developing countries.Findings suggest shared population-leveand perhaps local tissue drivers and highlight the value of integrated chronic disease prevention strategies. Cancer incidence shows a very strong global correlation with dementia incidence across 204 countries. The association remains robust after adjusting for economic affluence, urbanization, relaxed selection opportunity, and life expectancy. Cancer incidence explains substantially more variance in dementia incidence than traditional socioeconomic and demographic factors. The cancer–dementia relationship is consistent across most income groups and world regions, especially in upper-middle-income and developing countries. Findings suggest shared population-leveand perhaps local tissue drivers and highlight the value of integrated chronic disease prevention strategies.