Critical Illnesses May Promote Cognitive Decline Associated With Alzheimer Disease

Brain inflammation caused by critical illness and infection may lead to the observed reduction in brain volume.

Although it can’t yet be proven that brain structure changes and the acceleration of cognitive decline processes associated with Alzheimer disease are promoted by critical illness and major infection, a team of investigators at Johns Hopkins Medicine suggest that is the case.

In an assessment of the roles of hospitalization due to critical illness and major infection in brain structure changes, the Johns Hopkins investigators utilized data from the Atherosclerosis Risk in Communities Study (ARIC) to observe brain structure changes underlying cognitive decline and dementia in association with critical illness and infection.

In the ARIC study, nearly 16,000 participants aged 45 to 64 years old from Maryland, North Carolina, Minnesota, and Mississippi were originally enrolled, with data including magnetic resonance imaging (MRI) scans that showed brain structure in addition to a large cohort of participants followed over a 24-year period. Five medical exams and structured interviews were also included in the large cohort.

Due to the study’s long follow-up period, the team was able to obtain hospitalizations over many years, making the study especially rigorous since Alzheimer disease takes decades to evolve and time to diagnose, noted lead investigator Keenan Walker, PhD, postdoctoral fellow in the Department of Neurology at the Johns Hopkins University School of Medicine

In order to assess evidence of atrophy and damage to so-called white matter, Walker and his team focused on a subset of ARIC subjects who were administered a brain MRI during the final medical exam. A survey of medical records from hospital admissions throughout the ARIC study, 5 in-person exams, and annual telephone contact with participants were also used to collect data.

By using an internationally defined classification of disease codes (or ICD-9 codes) used for insurance billing purposes, the team identified critical illness that included shock, severe sepsis, acute respiratory failure, hypotension, respiratory or cardiac arrest, and the need for cardiopulmonary resuscitation prolonged ventilation.

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