Outcomes from various studies differ, and no definite conclusion is possible

Half of all people reaching the age of 65 subsequently have one or more operations,1 but despite substantial research on short term cognitive dysfunction within the first week after the operation little research has been undertaken into the potential long term effects on cognition. The exception is cardiac surgery, where cognitive dysfunction has been well documented and has usually been attributed to the adverse effects of cardiopulmonary bypass on the brain.2 3 Various risk factors for long term (defined as three months or more) postoperative cognitive dysfunction have been investigated, including type of anaesthetic agent, general versus regional anaesthesia, use of anticholinergic agents such as atropine, or the physiological effects of the anaesthetic such as hypoxia, hypotension, or hyper-ventilation.

The multicentre International Study of Post-Operative Cognitive Dysfunction (ISPOCD1) compared 1218 patients aged 60 years and older undergoing major surgery with a control group (n = 321) of a similar age.4 At three months after …