Two-fold setback: ICU stay doubles dementia risk

Intensive care unit (ICU) hospitalization doubles the risk of subsequent dementia in older adults,  a longitudinal study suggests.

Compared with older patients who were not confined to ICU, those who had an ICU experience were more likely to develop all-type dementia (hazard ratio [HR], 2.20, 95 percent confidence interval [CI], 1.75–2.77) or dementia (HR, 2.10, 95 percent CI, 1.66-2.65). [AAIC 2022, abstract 67719]

“ICU hospitalization due to critical illness, for example, severe COVID-19, has been linked to subsequent cognitive impairment in older patients,” said study author Dr Bryan James from Rush University in Chicago, Illinois, US at AAIC 2022. “Despite that, only a few studies have demonstrated that ICU hospitalization is related to long-term risk of developing Alzheimer’s and other age-related dementias. Given the high rate of ICU hospitalization in older persons, especially during the COVID-19 pandemic, it’s critical to explore this relationship,” he added.

Underrecognized risk factor

Patients usually acquired dementia after weeks of acute injury due to an illness, regardless of hospitalization history. “Just being critically ill makes you lose millions of brain cells. Soon, problems with memory and executive function set in, that on cognitive testing looks like Alzheimer’s disease,” commented Dr Wes Ely from the Vanderbilt University Medical Centre in Nashville, Tennessee, US, who is unaffiliated with the study. “You don't have to be in an ICU and on life support to get this.”

“ICU hospitalizations may be an under-recognized risk factor for dementia in older adults,” he added.

The brain, being a powerful tool with the capacity for neuroplasticity,  eventually improves with cognitive rehabilitation and exercise, be it Scrabble, Sudoku, or computerized brain games, said Ely.

Long follow-up

Patients included 3,822 older adults being treated at the Rush Alzheimer’s Disease Center without known dementia at enrolment. They were followed for an average of 7.8 years upon enrolment. Over half of them had an ICU stay: 27 percent before they enrolled in the Rush study and 25.1 percent during follow-up. The mean age of the patients was 73 years.

Incident Alzheimer’s and all-type dementia were assessed using standardized annual cognitive testing. Findings were adjusted for baseline measures of hypertension, diabetes, BMI, vascular risk factors, vascular disease burden, other chronic medical conditions, functional disabilities, depression, and physical activity.

James acknowledged that delirium was not assessed in the study. “But other studies have shown that experiencing delirium in the ICU does lead to a higher risk for long-term cognitive impairment.”

Other triggers could be sedation and severe sepsis, acute dialysis, and neurologic dysfunction, he added.

The analysis was not designed to look at specific modifiable factors to reduce dementia risk in ICU patients, but James said they are planning to investigate that next.