No convincing association between post-operative delirium and post-operative cognitive dysfunction: a secondary analysis

Background Post‐operative delirium and post‐operative cognitive dysfunction ( POCD ) are both common but it has not been clarified how closely they are associated. We aimed to assess the possible relationship in a secondary analysis of data from the ‘Surgery Depth of anaesthesia and Cognitive outcome’‐ study. Methods We included patients aged ≥ 60 years undergoing non‐cardiac surgery planned for longer than 60 min. Delirium was assessed according to the Diagnostic and Statistical Manual of Mental Disorders IV criteria in the post‐anaesthesia care unit ( PACU ) as well as within the first week after surgery. Cognitive function was assessed with a neuropsychological test battery. Multivariable analysis of POCD was performed with consideration of predisposing and precipitating factors. Results Of 1277 randomized patients, 850 (66.6%) had complete data. Delirium was found in 270 patients (32.9% of 850). We detected POCD in 162 (20.9% of 776) at 1 week and in 52 (9.4% of 553) at 3 months. In multivariable analysis ( n = 808), delirium had no overall effect on POCD ( P = 0.30). Patients with no delirium in PACU but with postoperative delirium within 7 days had an increased risk of POCD at 3 months ( OR = 2.56 (95%‐confidence interval: 1.07–6.16), P = 0.035). No significant association was found for the other subgroups. Conclusions There is no clear evidence that postoperative delirium is independently associated with POCD up to 3 months.