To quote from my article for August 2011,  “It is clear that anesthetic agents may be neurotoxic for some and more so after 60.”  This statement was predicated on findings from that time suggesting that undergoing general anesthesia may cause cognitive decline especially in the elderly.  Delirium and postoperative cognitive decline are the two most common untoward effects of surgery.  Delirium is transient and obvious but may last days to weeks.  Postoperative cognitive decline is a more long lasting condition, often subtle at first.

But not so fast, understanding is a process that evolves over time and must integrate new information as it becomes available.  A new study (Mayo Clinic Proceedings, May 2013) states that there is no association between anesthesia and dementia.  The data were obtained from medical records on nearly 2000 cases.  Results were based on individuals that were older than 45 when first undergoing their first anesthesia.

There was no association of anesthesia with dementia in this study.  Furthermore, there was no association between the number of procedures and the development of dementia.  The results were similar for those diagnosed with Alzheimer’s disease as for those with dementias from other causes.  There was also no association between either duration or type anesthetic agent used and development of dementia.

The authors of the study feel that it may not actually be the anesthesia that causes postoperative dementia but rather that postoperative dementias are a result of a preexisting but yet unrecognized cognitive decline.  Also supporting this idea is that there are enduring effects of hospital acquired delirium in patients that already are diagnosed with Alzheimer’s disease.  The rate of decline is about two times faster in those with Alzheimer’s who develop an in-hospital delirium when compared with those who do not.   Delirium is a transient condition that clears and returns affected persons to their baseline level of cognition.  Five years after hospitalization those with Alzheimer’s who developed delirium declined more quickly.  The delirium may be transient but the risk for more rapid decline is not.

The bottom line is that the association between anesthesia and risk for developing a dementia remains unresolved.  The anesthesia may not be the culprit.  What seems to be clear is that those with pre-existing cognitive decline, whether recognized or not, are at greater risk of bad outcomes (delirium or postoperative decline) than those who have intact cognitive functions. The decision of whether or not to have surgery under anesthesia remains complex as we age and needs to weight potential gains and costs.  The clearest advice is to avoid purely elective surgical procedures especially in the elderly and  if they are cognitively compromised.