Heterogeneity in multimorbidity patterns and chronic disease association rules among middle-aged and older adults with cognitive impairment: A dual-cohort analysis of community and hospital real-world data

Abstract Objective To compare chronic disease multimorbidity characteristics and association patterns in cognitively impaired middle‑aged and older adults across community and clinical settings, and to provide evidence for stratified chronic disease management. Methods A dual-database parallel controlled design was adopted, uniformly referencing the 15 categories of chronic diseases from the China Health and Retirement Longitudinal Study (CHARLS) database. After homogenization of the two datasets, descriptive statistics, independent sample t-tests, and chi-square tests were used to compare baseline characteristics and comorbidity burden between the two groups. The Apriori association rule algorithm was employed to mine comorbidity association patterns and core disease clusters in both populations. Results This study included 796 community-dwelling older adults with physician-diagnosed memory disorders and 543 inpatients with confirmed cognitive disorders hospitalized from 2019 to 2025. Significant inter-group differences existed in sociodemographics, sleep quality and chronic disease counts. The community group showed left-skewed distribution: 32.91% had no somatic chronic conditions, mild-to-moderate multimorbidity dominated with a balanced middle-peaked pattern. The hospital group had a right-skewed distribution, with over 85% having three or more somatic chronic conditions. Association analysis identified 46 community rules forming an inflammation-related respiratory-digestive-joint-cardiac cluster. A total of 170 hospital rules indicated severe multisystem multimorbidity with renal, hepatic and pulmonary target organ damage, including 44 rules with 100% confidence. Conclusion Cognitively impaired populations exhibit prominent setting-specific multimorbidity heterogeneity. Early screening for inflammatory risks is essential for community residents, while hospitalized patients require standardized lipid management and targeted organ damage prevention.