ICU Stays Linked to a Doubling of Dementia Risk

Older adults who have spent time in the intensive care unit (ICU) have double the risk of developing dementia in later years compared with older adults who have never stayed in the ICU, new research suggests.

“ICU hospitalization may be an under-recognized risk factor for dementia in older adults,” Bryan D. James, PhD, epidemiologist with Rush Alzheimer’s Disease Center, Chicago, Illinois, told Medscape Medical News.

“Healthcare providers caring for older patients who have experienced a hospitalization for critical illness should be prepared to assess and monitor their patients’ cognitive status as part of their long-term care plan,” James added.

The findings were presented at the Alzheimer’s Association International Conference (AAIC) 2022.

Hidden Risk Factor?

ICU hospitalization as a result of critical illness has been linked to subsequent cognitive impairment in older patients. However, how ICU hospitalization relates to the long-term risk of developing Alzheimer’s and other age-related dementias is unknown.

“Given the high rate of ICU hospitalization in older persons, especially during the COVID-19 pandemic, it is critical to explore this relationship, James said.

The Rush team assessed the impact of an ICU stay on dementia risk in 3822 older adults (mean age, 77 years) without known dementia at baseline participating in five diverse epidemiologic cohorts.

Participants were checked annually for development of Alzheimer’s and all type dementia using standardized cognitive assessments.

Over an average of 7.8 years, 1991 (52%) adults had at least one ICU stay; 1031 (27%) had an ICU stay before study enrollment; and 961 (25%) had an ICU stay during the study period.

In models adjusted for age, sex, education, and race, ICU hospitalization was associated with 63% higher risk of Alzheimer’s dementia (hazard ratio). [HR] 1.63; 95% CI, 1.41 – 1.88) and 71% higher risk of all-type dementia (HR, 1.71; 95% CI, 1.48 – 1.97).

In models further adjusted for chronic other health factors such as vascular risk factors and disease, other medical conditions and functional disabilities, the association was even stronger: ICU hospitalization was associated with roughly double the risk of Alzheimer’s dementia (HR 2.10; 95% CI, 1.66 – 2.65 and all type dementia (HR, 2.20; 95% CI, 1.75 – 2.77).

James told Medscape Medical News it remains unclear why an ICU stay may raise the dementia risk.

“This study was not designed to assess the causes of the higher risk of dementia in persons who had ICU hospitalizations. However, researchers have looked into a number of factors that could account for this increased risk,” he explained.

One is critical illness itself that leads to hospitalization, which could result in damage to the brain; for example, severe COVID-19 has been shown to directly harm the brain, James said.

He also noted that specific events experienced during ICU stay have been shown to increase risk for cognitive impairment, including acute infection and severe sepsis, dialysis, neurologic dysfunction and delirium, and sedation.

Important Work

Commenting on the study for Medscape Medical NewsHeather Snyder, PhD, vice president of medical & scientific relations at the Alzheimer’s Association, said what’s interesting about this study is that it looks at individuals in the ICU, regardless of the cause.

“The study shows that having some type of health issue that results in some type of ICU stay is associated with an increased risk of declining cognition,” Snyder said.

“That’s really important,” she said, “especially given the increase in individuals, particularly those 60 and older, who did experience an ICU stay over the last couple of years and understanding how that might impact their long-term risk related to Alzheimer’s and other changes in memory.”

“If an individual has been in the ICU, that should be part of the conversation with their physician or healthcare provider,” Snyder advised.

The study was funded by the National Institute on Aging. James and Snyder have disclosed no relevant financial relationships.

Alzheimer’s Association International Conference (AAIC) 2022: Abstract 67719. Presented July 31, 2022.

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