PROVIDENCE, R.I. — A new study has found that postoperative delirium—a sudden state of confusion, agitation, and reduced attention that can occur after surgery involving anesthesia—remains the strongest predictor of long-term cognitive decline in older adults.

Researchers from Brown University, Mass General Brigham, and Hebrew SeniorLife investigated whether factors such as illness, frailty, or rehospitalizations could account for the link between delirium and declining cognitive health. While rehospitalizations, intensive care admissions, and post-acute rehabilitation stays were associated with worsening cognition over time, they did not explain the significant impact of delirium on long-term brain function.

“Demonstrating that individuals who develop postoperative delirium experience a more rapid cognitive decline than those who do not—and that this decline cannot be explained by rehospitalizations—highlights the urgent need to better understand and prevent delirium in older adults,” said Dr. Zachary J. Kunicki, assistant professor of psychiatry and human behavior at Brown University’s Warren Alpert Medical School and co-first author of the study.

The findings were published in the journal JAMA Internal Medicine.

Delirium is the most common postoperative complication among older adults and has been linked to a range of adverse outcomes, including reduced physical function, long-term cognitive impairment, and dementia. It can also trigger a cycle of additional hospitalizations, often involving intensive care or rehabilitation services.

“We observed that delirium was associated with cognitive decline at a rate exceeding what is typically seen in mild cognitive impairment, and this effect was not driven by rehospitalizations,” said co-first author Dr. Tammy T. Hshieh, a geriatrician at Mass General Brigham. “This was unexpected, as we anticipated that rehospitalizations would account for at least part of the relationship between delirium and long-term cognitive decline. More research is needed to better understand the mechanisms connecting delirium and brain health.”

The study analyzed data from the Successful Aging after Elective Surgery (SAGES) project, which followed 560 adults aged 70 and older. Participants underwent cognitive assessments every six months for the first three years and annually thereafter for up to six years. Researchers used a comprehensive battery of 11 cognitive tests to evaluate changes in cognitive function over time.

Results showed that postoperative delirium was linked to accelerated cognitive decline lasting up to five years after surgery. Although each rehospitalization was associated with additional cognitive deterioration, delirium remained an independent and more powerful predictor of long-term decline. Patients who experienced delirium were also more likely to be rehospitalized.

Contrary to expectations, accounting for rehospitalizations did not significantly alter the relationship between delirium and cognitive decline. The researchers emphasized the need for future studies to uncover the biological and clinical mechanisms underlying this association.

“We expected that at least some of delirium’s impact on long-term cognition could be explained by rehospitalizations related to serious medical conditions,” said senior author Dr. Sharon K. Inouye, professor of medicine at Harvard Medical School and director of the Aging Brain Center at Hebrew SeniorLife’s Hinda and Arthur Marcus Institute for Aging Research. “However, we were surprised to find that rehospitalizations did not account for the cognitive effects observed following delirium.”

According to Kunicki, the findings further strengthen the contributions of the SAGES project, led by Inouye.

“SAGES is among the longest-running delirium cohort studies in the world,” Kunicki said. “Our previous research has shown that postoperative delirium is associated with accelerated cognitive decline, and the study has contributed to more than 100 scientific publications focused on delirium.”

Source: https://www.brown.edu/news/2026-06-08/postoperative-delirium-cognitive-decline