More than 77% of people in the US had been infected with SARS-CoV-2 as of 2022.¹ Of these, approximately 30% of survivors report having persistent symptoms classified as long COVID² and 11% describe persistent symptoms at 6 months.³

Patients frequently complain of brain fog, cognitive difficulties, and other neurologic sequelae as the primary drivers of decreased quality of life. These patients also perform worse in cognitive measures of working memory, attention, and processing speed compared to controls.⁴

A recent study that gave cognitive assessments to more than 100,000 people with and without long COVID confirmed that complaints of brain fog in long COVID patients were correlated with lower cognitive performance in memory, reasoning, and executive function tasks.⁵ Although mRNA vaccines against SARS-CoV-2 have been extremely effective in preventing severe acute disease, the incidence of long COVID has not significantly decreased in the US despite widespread vaccine uptake.⁶ This indicates that long COVID, also referred to as postacute sequelae of SARS-CoV-2 infection, will remain a medical concern for the foreseeable future.

As a result, it is important that surgeons become familiar with this syndrome in order to continue providing the best care for their patients.

How Does Surgery Affect Cognition?

The lay press is filled with stories of patients who were “never the same” after surgery.⁷ Patients describe cognitive deficits in focus, memory, and attention, all affecting their ability to function.⁸ Data suggest that approximately 10% to 12% of patients suffer cognitive dysfunction that persists up to 3 months postoperatively.⁹

In 2015, the American Society of Anesthesiologists launched the Brain Health Summit, with participation from the ACS, to discuss the state of the science of perioperative cognition.¹⁰ Subsequently, a working group proposed new nomenclature to better align perioperative terminology to diagnoses already used in medical fields.¹¹

For example, the term “postoperative cognitive dysfunction” had no consensus definition and was primarily used in research, disconnected from patients’ real-world experiences. The currently recommended term for cognitive impairment identified during the overarching perioperative period is “perioperative neurocognitive disorder,” with specific subclassifications defined by timing (see Table).

Postoperative delirium deserves special attention, as it may occur as a common complication distinct from other perioperative neurocognitive disorders. It is characterized by an acute onset of waxing and waning confusion, with changes in the levels of consciousness, attention, orientation, and disorganized thinking. The clinical presentation differs according to psychomotor subtype, ranging from hypoactive (e.g., slowed movements, quiet affect—symptoms that are easy to miss) to hyperactive delirium (e.g., restlessness and agitation), as well as mixed subtypes.

The rate of postoperative delirium across the literature is highly variable from 5% to 52%¹² and dependent on the detection method (from prospective screening using validated tools to retrospective chart reviews using keywords). However, there is some evidence that rates vary by specialty and operative stress load.^13,14

Across multiple studies, common risk factors include age, preexisting cognitive impairment, previous episodes of postoperative delirium, and low education levels. Despite recommendations from the ACS and American Geriatrics Society to perform routine screening for baseline cognition,¹⁵ this is rarely performed.

The lack of baseline data can lead to a true “blind spot” in the ability of clinicians to best identify, educate, and enact preventive measures for patients at highest risk for postoperative delirium. Unfortunately, patients who suffer delirium, particularly when combined with surgical complications, experience prolonged length of stay, higher hospitalization costs, need for institutional discharge, and even face long-term consequences.^16,17

Growing evidence suggests that postoperative delirium is associated with long-term cognitive decline, both for those with normal cognition at baseline and those with preexisting dementia.¹⁸ The Successful Aging after Elective Surgery study cohort has demonstrated a dose-response relationship wherein higher severity delirium is associated with worse cognitive outcomes.¹⁹ Furthermore, these effects persist up to 6 years, with delirium accelerating cognitive decline by 40% over normal aging-related changes.²⁰

Whether preceded by delirium or not, postoperative neurocognitive disorders can significantly decrease long-term health and quality of life. Patients with postoperative neurocognitive disorders are twice as likely to experience impaired instrumental activities of daily living.²¹ Furthermore, cognitive and functional decline are associated with higher rates of long-term mortality and healthcare utilization.²²