Effect of preoperative pain and depressive symptoms on the risk of postoperative delirium: a prospective cohort study

Background Preoperative pain and depression predispose patients to delirium. We investigated whether pain and depressive symptoms interact to increase the risk of delirium.Methods We enrolled 459 people without dementia, who were aged 70 years or older and were scheduled for elective orthopaedic surgery between June, 2010, and August, 2013. At baseline, participants reported their current pain and the average and worst pain in the previous 7 days, on a scale of 0-10. Depressive symptoms before surgery were assessed with the 15-item geriatric depression scale and chart. Delirium after surgery was assessed with the confusion assessment method and chart. We used multivariable analysis to assess the relation between preoperative pain and postoperative delirium stratified by the presence of depressive symptoms.Findings Delirium was reported in 106 (23%) of patients, and was significantly more frequent in those with depressive symptoms at baseline than in those without (relative risk [RR] 1.6, 95% CI 1.2-2.3). Preoperative pain was associated with an increased adjusted risk of delirium across all pain measures (RR 1.07-1.08 per 1-point increase in pain). In stratified analyses, patients with depressive symptoms had a 21% increased risk of delirium for each 1-point increase in worst pain score, which indicated a significant interaction (p(interaction)=0.049). Similarly, a 13% increased risk of delirium was seen per 1-point increase in average pain score, but the interaction was not significant.Interpretation Preoperative pain and depressive symptoms are associated with increased risk of delirium, independently and with substantial interaction, which suggests a cumulative effect. These factors should be assessed before surgery.