A Pain Medicine News report indicates that poor preoperative sleep is associated with greater pain and poor functional outcomes as long as 12 months after total knee replacement.

To help determine the relationship between preoperative sleep quality and postoperative pain, Dr. Campbell and her co-investigators enrolled 164 total knee replacement patients (mean age, 66 years; 60% women) into the trial. Participants completed a battery of questionnaires and assessment procedures before surgery and six weeks and three, six and 12 months postoperatively.

Pain intensity was measured using the Brief Pain Inventory, and nightly sleep duration was assessed with the Pittsburgh Sleep Quality Index. Function was measured using the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Mental depression levels were determined with questions from the Patient Reported Outcomes Measurement Information System.

As Dr. Campbell reported at the 2015 annual meeting of the American Pain Society (abstract 350), the study’s most telling findings were of predictors of postoperative pain. The investigators found that shorter preoperative sleep duration was significantly associated with average pain severity three months after surgery (P<0.05), even after controlling for age, baseline depression and pain scores. Preoperative sleep duration did not predict pain at six months after surgery, but was marginally associated with pain at 12 months. Shorter sleep duration six weeks after surgery also significantly predicted greater pain at three, six and 12 months after surgery (P< 0.05), adjusting for the same covariates.

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