Editors' note: Neuroimaging findings in midlife and risk of late-life dementia over 20 years of follow-up

Abstract

Using prospective observational data collected in the Atherosclerosis Risk in Communities (ARIC) Study, Dr. West and colleagues sought to estimate the risk of long-term dementia in 1,881 stroke-free patients based on early MRI abnormalities. Nearly 15% of included patients developed dementia over the 20-year observational period. Unsurprisingly, there was a significantly greater risk of all-cause dementia among patients with high-grade microvascular ischemic changes and ventricular dilatation. This effect persisted after adjustment for known dementia risk factors including older age, sex, race/ethnicity, history of hypertension and diabetes, tobacco use, and APOE e4 status. Among the study limitations, however, is that only two-thirds (67%) of the eligible ARIC participants completed the MRI assessment for this study. And of these patients, a dementia diagnosis could only be assessed in 539 patients (29% of the imaged cohort, 539/1881 patients). Although the association between the aforementioned clinical and radiographic biomarkers for later dementia might not be significantly influenced by this selection bias, the incidence rate of 20-year dementia in patients with these risk factors could certainly be. In response to this article, Drs. Lattanzi and Silvestrini also note that blood pressure variability could have behaved as a mediator between the various MRI abnormalities and incident dementia. Furthermore, if treated throughout the study period, blood pressure lability might have been a modifiable risk factor for dementia in this cohort. Dr. West acknowledges that this will be explored in a separate analysis. Using prospective observational data collected in the Atherosclerosis Risk in Communities (ARIC) Study, Dr. West and colleagues sought to estimate the risk of long-term dementia in 1,881 stroke-free patients based on early MRI abnormalities. Nearly 15% of included patients developed dementia over the 20-year observational period. Unsurprisingly, there was a significantly greater risk of all-cause dementia among patients with high-grade microvascular ischemic changes and ventricular dilatation. This effect persisted after adjustment for known dementia risk factors including older age, sex, race/ethnicity, history of hypertension and diabetes, tobacco use, and APOE e4 status. Among the study limitations, however, is that only two-thirds (67%) of the eligible ARIC participants completed the MRI assessment for this study. And of these patients, a dementia diagnosis could only be assessed in 539 patients (29% of the imaged cohort, 539/1881 patients). Although the association between the aforementioned clinical and radiographic biomarkers for later dementia might not be significantly influenced by this selection bias, the incidence rate of 20-year dementia in patients with these risk factors could certainly be. In response to this article, Drs. Lattanzi and Silvestrini also note that blood pressure variability could have behaved as a mediator between the various MRI abnormalities and incident dementia. Furthermore, if treated throughout the study period, blood pressure lability might have been a modifiable risk factor for dementia in this cohort. Dr. West acknowledges that this will be explored in a separate analysis.