Study links dementia-related brain changes to hospital stays for critical illness

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An analysis of electronic health records and MRI scans by Johns Hopkins researchers indicates that hospitalization, infection and critical illness influence changes in brain regions that underlie dementia.

Researchers leveraged data from the Atherosclerosis Risk in Communities (ARIC) study, a rich dataset that included MRI scans showing brain structure as well as social, demographic and hospital information for a large cohort of participants who were followed over a 24-year period that included five medical exams.

Their study, published recently in the Journal of the American Geriatrics Society, focused in particular on a subset of more than a thousand ARIC patients who received a brain MRI during the final medical exam in the study to look at evidence of atrophy and damage to so-called white matter—the part of the brain responsible for transmitting messages.

“Whereas all‐cause hospitalization was primarily associated with lower white matter integrity, critical illness and major infection were associated with smaller brain volume, particularly within regions implicated in (Alzheimer’s disease),” conclude the study’s authors.

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Keenan Walker, lead author and a postdoctoral fellow in the Department of Neurology at the Johns Hopkins University School of Medicine, contends that the study is “one of the first to look specifically at how both critical illness and infection might promote brain changes that set the stage for late-life cognitive decline and serve as independent risk factors for dementia.”

Their analysis of 1,689 participants found that 1,214 (72 percent) were hospitalized, 47 (4 percent) had a critical illness, and 165 (14 percent) had a major infection. In addition, researchers discovered that hospitalization during the follow-up period—regardless of the reason—was associated with 9 percent greater white matter hyperintensity volume and significantly lower integrity of white matter microstructure.

For the 1,214 hospitalized patients, the study demonstrated that those who had one or more critical illness had a 3 percent smaller brain volume in brain regions that are implicated in Alzheimer's disease. Major infection was also linked with both smaller brain volume in regions vulnerable to Alzheimer's disease (2 percent smaller) and 10 percent larger brain ventricle volume.

“It suggests that these illnesses may actually have an effect on brain structure and therefore brain function,” says Walker, who adds that, going forward, researchers will assess how hospitalization is associated with inflammation in the brain and how it might lead to a reduction in brain volume.

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