It is true that older patients who have major surgery, such as a cardiac bypass or joint replacement, may experience some decrease in cognitive function. This condition is called Postoperative Cognitive Decline (POCD) and it occurs in approximately 10 to 20 percent of elderly patients after joint-replacement surgery. Its not yet clear what is responsible for the decline, but some causes may include an inflammatory response to surgery or the effects of anesthesia. Potential risk factors for the development of this problem include the preoperative cognitive status of the patient, operative events related to the surgery itself, and anesthetic agents. Most often, POCD takes the form of mild forgetfulness and usually improves with time. Some mental decline also may be due to medications prescribed after surgery, and this generally improves with a cessation or change of medication.