Perioperative Brain Health Centre
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Cognitive decline after anesthesia

Anesthesia and surgery

  • Anesthesia causes three effects that allow patients to tolerate surgery: unconsciousness, memory loss and prevents unwanted movements.
  • Many patients may have cognitive issues for weeks to months after even a single anesthetic exposure.

Types of cognitive symptoms after surgery

Postoperative delirium (POD) is a shift in consciousness soon after surgery.
Symptoms of POD are:

  • Confusion
  • Trouble paying attention
  • Trouble with clear thinking
    • Hallucinations during POD lasts 1-3 days.

Neurocognitive Disorder (NCD) is a more long-term state in which a patient’s memory and learning decline after surgery.

  • NCD lasts weeks to months.


  • Poor memory (going into a room and not remembering why you are there)
  • Misplacing things
  • Inability to do routine tasks
  • Trouble with doing more than one thing at a time
  • Issues with mental tasks (solving crosswords, reading, etc.)
  • Difficulties understanding spoken language

Symptoms vary among patients and can range from mild to severe. Each person will have a different experience.

Risk factors

  • Cognitive decline can affect anyone who has surgery.
  • Commonly used anesthetics are linked with cognitive decline.
  • General anesthetics have the most impact.
  • NCD and POD share similar risk factors: age, fewer years of education and having two or more chronic diseases/conditions at the same time.
  • Older adult patients (65+) and patients who will have heart surgery are at the highest risk


  • NCD is NOT dementia.
  • NCD symptoms often do not present until long after surgery.
  • NCD is diagnosed with neurocognitive tests.
  • There are no medications to stop this.
  • 1 out of 3 patients will have NCD after they leave the hospital.
  • 1 to 6 patients out of 100 who have heart surgery will have cognitive decline.
  • POD occurs in 15 per cent to 53 per cent of older patients after surgery.


  • Exact cause of NCD is unknown.
  • Cognitive decline can last days to months, and in a few cases, persists for years.
  • NCD often resolves itself as normal brain function returns within a few months following hospital discharge for most patients.

No treatment available.

Healthy brains, healthy minds: minimizing your risk factors

There are many ways patients and their families can help to avoid cognitive decline.

  • Stay physically active
  • Follow a healthy diet
  • Take prescribed medications
  • Using all assistive devices such as hearing aids, glasses, etc.
  • Get enough sleep
  • Have support from family members to lower anxiety and help with key reminders

Cognitive decline: decline in memory, thinking, learning and decision-making time.

To learn more:

  • Visit the Perioperative Brain Health Centre 
  • The Globe and Mail: Silent strokes after elective surgeries in older adults double their risk of later cognitive decline. Health and Fitness, August 15th
  • CBC News: Under the knife and unaware? What happens when we're under anesthesia. The Current, June 25th
  • The Globe and Mail: I’m having memory problems after anesthetic and surgery. Is that common?” Life, March 12th
  • CODEX trial, Perioperative Brain Health Centre, Sunnybrook Health Sciences Centre, Clinical Trial Registry: NCT04289142
  • COGNIGRAM trial, Perioperative Brain Health Centre, Sunnybrook Health Sciences Centre, Clinical Trial Registry: NCT 03147937

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Written by: Lilia Kaustov (PhD) and Dr. Stephen Choi (MD, MSc, FRCPC)