Pre-surgical memory performance predicts chronic postsurgical pain up to 12 months later

This new research could help surgeons learn more about the patient’s brain before operating.

Patients who recall a greater number of specific “pain memories” before surgery are significantly less likely to develop chronic postsurgical pain up to one year later, indicates a study published in the journal PAIN authored by a team of researchers at York University and the Toronto General Hospital.

Chronic postsurgical pain is a major health problem and a common adverse effect of surgery. According to Dr. Hance Clarke, director of Pain Services at the Toronto General Hospital and co-author of “Autobiographical Memory Predicts Postsurgical Pain up to 12 Months after Major Surgery,” between five and 10 per cent of patients develop chronic postsurgical pain each year.

“That’s far too many, which is why we developed the Transitional Pain Service to treat high risk patients before surgery. But we need to know which factors to target in order to prevent long term pain.”

Joel Katz (2021 image)
Joel Katz

The study’s authors wondered whether autobiographical memory might be a risk factor for the development of chronic postsurgical pain. Anna Waisman, the lead author of the study and a master’s student studying with York University Professor Joel Katz, said autobiographical memory is a type of long-term memory that involves the ability to recollect personal life events and relevant factual information.

“Two cross-sectional studies found that people with chronic pain tended to recollect personal memories that are less specific than people without chronic pain,” says Waisman, “but no one had looked at this prospectively, to see if the memory bias occurs before the pain develops.”

The research team studied autobiographical memory in 97 patients scheduled for major surgery and followed them up for a year with assessments one, three, six and 12 months after surgery.  Participants were asked to remember personal events in response to positive cue words (like safe, delighted, relaxed) and pain-related cue words (like hurt, aching, sore).

Memories were coded in several ways; first the researchers looked at the specificity of the memories. Specific memories were defined as events that had occurred within a distinct spatiotemporal context lasting less than 24 hours (e.g., “My hips were aching Sunday from stretching”). Overgeneral memories were defined as events extending beyond a single day (e.g., “I’ve been relaxed the last three weeks”), categories of repeated events (e.g., “My legs always become sore after playing squash”), and general knowledge about the self or the world (e.g., “I’ve always been sensitive to pain”). The researchers also timed how long it took participants to begin to generate each memory and coded the memories according to whether they were related or unrelated to surgery.

“The number of specific memories the participants recalled before surgery predicted lower odds of reporting pain across all timepoints,” says Waisman. “And participants who took longer to recall memories in response to pain word cues before surgery, as well as those who generated more surgery-related content at the one-month postsurgical assessment, had greater odds of reporting postsurgical pain up to 12 months later.”

“These results tell us that the memory biases precede the development of chronic postsurgical pain, but we still don’t know if they’re causing it or simply correlated with it,” says Katz, Canada Research Chair in Health Psychology at York University and the senior author of the study. “This is a critical issue because if the biases are causally related to the pain, we can begin to develop and apply memory interventions to people who are awaiting surgery to reduce the risk that acute postsurgical pain becomes chronic.”

Find the study online.