A new study has found increasing evidence that delirium in older surgical patients may be associated with long-term cognitive decline.
Delirium is a common, serious, often fatal disorder affecting as many as 50 percent of older people during the course of surgery or hospitalization and costs more than $164 billion a year.
The new study, conducted by researchers at the Harvard Medical School-affiliated Hebrew SeniorLife Institute for Aging Research, Beth Israel Deaconess Medical Center, Brown University, and Northeastern University, examined the trajectory of short-term and long-term cognitive decline in patients who experienced delirium following a surgery.
The 560 participants in the study were aged 70 years or older, had no previous signs of dementia, and were scheduled to undergo surgery with an anticipated stay in the hospital of three days or greater, the researchers note.
Delirium occurred in 134 of the original 560 participants in the study. Both groups of participants, those who experienced delirium and those who did not, showed a significant cognitive decline at one month, followed by a recovery above baseline at two months and then a gradual decline for the next 34 months.
The delirium group, however, had a significantly greater decline at one month compared to those without delirium. Although they too recovered at two months, these patients had a more significant decline after the two-month mark than the non-delirium group.
Beyond two months, both groups declined on average, but the delirium group declined significantly more, according to the study’s findings.
When researchers compared changes from baseline to 36 months, there was no significant change for the group who did not experience delirium, but a marked decline for those who did.
According to the researchers, the fact that both the delirium and non-delirium groups suffered cognitive decline at month one, and then a return to baseline at month two, likely represents the immediate impact of anesthesia, surgery, and hospitalization. However, the higher rate of cognitive decline after the first month for those with delirium suggests that delirium may set off a cascade of events that leads to progressive, long-lasting effects, the researchers said.
Another possibility is that delirium is associated with a pre-existing higher rate of cognitive decline that is not detectable at baseline, the researchers said. In either case, delirium may serve as a marker for seniors with poor cognitive reserve.
“This study is highly significant in demonstrating that delirium is associated with subsequent long-term cognitive decline at a pace similar to that of mild cognitive impairment, even in those with normal cognitive function at baseline,” said Sharon K. Inouye, M.D., M.P.H., director of the Aging Brain Center at the Institute for Aging Research and professor of Medicine at Harvard Medical School.
“Whether or not delirium is causative, it identifies those at risk for subsequent cognitive decline and warrants both close clinical follow-up and preventive interventions.”
The study was published in Alzheimer’s & Dementia: The Journal of the Alzheimer’s Association.