PROVIDENCE, R.I. [Brown University] — Developing postoperative delirium — a sudden, significant state of confusion, agitation and inattentiveness that arises after surgery under anesthesia — remains the strongest predictor of long-term cognitive decline, a new study found.
Researchers from Mass General Brigham, Hebrew SeniorLife and Brown University followed older adults after surgery to determine if illness and frailty might explain part of the effect of delirium on cognitive decline. The researchers found that while rehospitalizations and intensive care or post-acute rehabilitation stays were associated with long-term cognitive decline, they do not help to explain the effect of delirium on long-term brain health.
“Showing that people who develop postoperative delirium decline at a faster pace than those who do not, and this faster decline is not explainable by rehospitalizations during follow-up, reinforces the crucial need to better understand and prevent delirium in older adults," said Zachary J. Kunicki, an assistant professor of psychiatry and human behavior at Brown University’s Warren Alpert Medical School who was a first author on the study.
The results were published in JAMA Internal Medicine.
Delirium is the most common post-operative complication in older adults and is associated with poor outcomes, including functional decline, long-term cognitive decline and dementia. It can lead to a cascade of rehospitalizations, including potential stays in the intensive care unit, post-acute care unit or both.
“We saw that delirium was associated with cognitive decline at a rate faster than what we would normally see with mild cognitive impairment, and the effect was not mediated by rehospitalization,” said co-first author Dr. Tammy T. Hshieh, a geriatrician at Mass General Brigham. “This was surprising because we thought rehospitalization would explain at least some of the effect of delirium on long-term cognitive decline. Future work needs to be done to better understand the important connections between delirium and long-term brain health.”
The study looked at data from the Successful Aging after Elective Surgery (SAGES) study, which followed 560 adults aged 70 years and older, measuring their cognition every six months for 36 months and then annually afterwards for up to six years. Using a detailed series of 11 cognitive tests, investigators found that cognitive changes after surgery are complex and that delirium influences cognition up to five years after it occurs. Each rehospitalization was associated with cognitive decline, and delirium was associated with more marked cognitive decline per year. Rehospitalizations were more common among patients who developed delirium.
Contrary to the researchers’ expectations, rehospitalization did not significantly change the impact of delirium on long-term cognitive decline. The researchers note that future work is needed to understand the mechanisms that explain why delirium is associated with long-term cognitive decline.
“We had anticipated that at least part of the effect of delirium on long-term cognition would be due to rehospitalizations which reflected serious medical conditions,” said senior author Dr. Sharon K. Inouye, a professor of medicine at Harvard Medical School and director of the Aging Brain Center at Hebrew Senior Life’s Hinda and Arthur Marcus Institute for Aging Research. “However, we were surprised to learn that rehospitalizations did not explain the effects of delirium on subsequent cognitive decline.”
Kunicki said the findings build on the work of the SAGES team, which Inouye leads.
“SAGES is one of the longest cohort studies on delirium in the world,” Kunicki said. “In our previous work, we have identified that postoperative delirium is associated with accelerated cognitive decline, and SAGES is associated with well over 100 manuscripts on delirium.”
Other study authors included Tamara G. Fong, Edward R. Marcantonio, Eva Schmitt, Guoquan Xu and Richard N. Jones. The study was funded by National Institute on Aging (R03AG075434, P01AG031720, R33AG071744).