Chronic conditions, multimorbidity, and its trajectory in relation to incident dementia: a prospective study

Abstract

AbstractBackgroundMany single chronic conditions and multimorbidity have been related to dementia in previous studies. However, the long‐term relation of multimorbidity and its developmental trajectory with dementia remains unclear.MethodThe study included 5,998 dementia‐free participants (58.9% female, mean [standard deviation] age = 73.5 [6.8] years) from the Health and Retirement Study. Data on the health status, including self‐reported diagnosis of eight chronic conditions (high blood pressure, diabetes, cancer, lung diseases, heart diseases, stroke, psychological disorders, and arthritis) were collected from 1994 to 2008. Trajectories of multimorbidity development (including “no new condition, 31.2%”, “slow growth, 25.1%”, “steady growth, 32.2%”, and “rapid growth, 11.4%”) were identified using group‐based trajectory modeling methods. Incident dementia were detected during 2008 to 2018. Cox proportional hazard models were used to assess the relations of number of chronic diseases and its developmental trajectory to dementia.ResultDuring the study follow‐up (median [IQR] = 8 [6‐10]), a total of 741 (12.3%) participants developed dementia. Number of chronic conditions was associated with risk of subsequent dementia (hazard ratio [HR] for per condition increment = 1.14; 95% confidence interval [CI] = 1.08 to 1.20). The associations were consistently observed across major study subgroups. Psychological disorders (HR = 1.72, 1.42 to 2.08) and stroke (HR = 1.64, 1.32 to 2.02) demonstrated the strongest relations, followed by diabetes (HR = 1.23, 1.03 to 1.48) and heart diseases (HR = 1.21, 1.03 to 1.43). Moreover, participants with “rapid growth” trajectory of multimorbidity development were observed to have the highest dementia risk (HR = 1.38, 1.09 to 1.76), compared to the “no new condition” group.ConclusionOur study provided evidence that the number of coexisting conditions and the faster development of multimorbidity were both associated with higher risk of subsequent dementia. Further investigations are warranted to understand the underlying mechanisms.