Older adults who stay longer in the intensive care unit (ICU) are associated with an increased risk of Alzheimer’s disease and all-type dementia, according to a new study presented at the 2022 Alzheimer’s Association International Conference in San Diego, California.
Using a diverse group of older patients without known dementia, the long-term study showed those who experienced ICU hospitalization had double the risk of getting Alzheimer’s disease (AD) and dementia of any type in later years compared to older adults who have never stayed in the ICU.
“Given the high rate of ICU hospitalization in older persons, especially during the COVID-19 pandemic, it is critical to explore this relationship,” said Bryan James, PhD, lead author of the study and associate professor at Rush Medical College. “ICU hospitalizations may be an under-recognized factor for dementia in older adults.”
ICU hospitalizations may be an under-recognized factor for dementia in older adults.
James and his colleagues analyzed 3,822 older adults with an average age of 77 years old with no dementia at the start of the study to assess the impact of an ICU stay on dementia risk. The participants were also checked every year for the development of AD and all-type dementia using standardized cognitive tests.
Once the researchers adjusted for factors like sex, education and race, they found ICU hospitalization was associated with a 63% higher risk of Alzheimer’s and a 71% higher risk of all-type dementia.
In another analysis where researchers adjusted for hypertension, diabetes, body mass index, vascular disease, depression, physical activity and other medical conditions, ICU hospitalization was associated with nearly double the risk of developing AD and all-type dementia.
James said that even though a large body of research demonstrates that many patients, especially older patients who survive ICU hospitalization, may experience significant cognitive impairment, this study specifically shows an association between ICU stays and other dementias.
“This study is unique in showing that ICU hospitalization is associated with the development of Alzheimer’s and other late-life dementias in subsequent years after the ICU stay using standard criteria for assessing these conditions in older persons,” James said. “This study’s design allowed for the comparison in risk of developing dementia for older persons who experienced an ICU hospitalization compared to those who did not.”
He noted that while the data was collected before the COVID-19 pandemic, the findings are still relevant to understanding what could happen in the years after this pandemic due to the increased rate of ICU hospitalizations, especially in older patients.
Why might ICU hospitalizations be linked to Alzheimer’s and dementia?
“The study was not designed to assess the causes of the higher risk of dementia in persons who had ICU hospitalizations,” James said. “However, researchers have looked into a number of factors that could account for this increased risk.”
One factor could be that the critical illness itself that causes an ICU stay may result in damage to the brain, said Dr. E. Wesley Ely, MD, MPH, professor of medicine at Vanderbilt Memory & Alzheimer’s Center and an ICU physician at Vanderbilt University Medical Center in Nashville.
“When you’re in the ICU and or the hospital itself and have infections or diseases like sepsis, what happens is that we get problems with blood flow to our brain,” he said. “We also sometimes have low oxygen levels and we receive medications, which are dangerous to our brain. The combination of these things poses a very high risk for neurological injury.”
Ely added that people can also become delirious during a hospital stay, and the longer you’re delirious, the higher the risk of having long-term acquired dementia.
“Every additional day of delirium increases your risk of dying by about 10% and it increases your risk of long-term cognitive impairment by about 30%,” Ely said, “so you can see that even short durations of delirium of one to three days pose very great risks for people who are hospitalized and in the ICU.”
Added factors like immobilization, overuse of sedatives and absence of family could be other potential reasons, Ely said.
“If you do things like sedate somebody, immobilize them and don’t have family around to help orient them, they have more delirium,” he explained. “And delirium is a big risk factor for this onset of dementia.”
What can you do to minimize your risk of ICU hospitalizations, AD and dementia?
Critical illness and ICU hospitalization can result in severe damage to the brain for many patients that unfortunately may not be fully remedied by any activities, James said. However, many people who are discharged from the ICU can benefit from staying physically, mentally and socially active.
People who are discharged from the ICU can benefit from staying physically, mentally and socially active.
“Family engagement and staying as active as possible also appear to be important to decreasing risk of cognitive problems after an ICU stay,” he noted. “Both the patient and family members should be aware of cognitive changes in ensuing years and communicate with their doctor and health care teams.”