Does exposure to general anesthesia cause dementia?

In a word, “No.”


A landmark study published in Anesthesiology Dokkedal U et al, Cognitive Functioning after Surgery in Middle-aged and Elderly Danish Twins. Anesthesiology. 2016 Feb;124(2):312-21  answers this question. Dokkedal studied 8,503 middle-aged and elderly Danish twins. Results from cognitive tests were compared in twins in which one sibling was exposed to surgery and the other was not. A history of major surgery was associated with a negligibly lower level of cognitive functioning, but there was no difference by interpair analysis, that is, when compared to their twin. There was no clinically significant association of major surgery and anesthesia with long-term cognitive dysfunction, suggesting that factors other than surgery and anesthesia, such as preoperative cognitive functioning and underlying diseases, were more important for cognitive functioning in mid- and late life than surgery and anesthesia.

(For readers who are not medical professionals, cognitive function includes reasoning, memory, attention, and language, the attainment of information and, thus, knowledge. Alzheimer’s disease and dementia equate to a chronic loss of these cognitive functions.)

Because Dokkedal’s study looked at a large number of patients, and each of these patients had a twin, it is considered a statistically powerful study.

A second recent study published in the same month, (Sprung J et. al., Association of Mild Cognitive Impairment With Exposure to General Anesthesia for Surgical and Nonsurgical Procedures: A Population-Based Study. Mayo Clin Proc. 2016 Feb;91(2):208-17)  examined 1731 Minnesota residents aged 70 – 89. Of these, 536 out of the 1731 developed Mild Cognitive Impairment (MCI) during a median follow-up of 4.8 years. All of their anesthesia records for surgeries after the age of 40 were reviewed. The authors found no significant association between the cumulative exposure to surgical anesthesia after 40 years of age and the development of Mild Cognitive Impairment.

In an editorial accompanying the Dokkedal study, (Avidan MS, Evers AS, The Fallacy of Persistent Postoperative Cognitive Decline, Anesthesiology. 2016 Feb:124(2);255-258.) Avidan and Evers wrote, “It is similarly tragic when adults older than 50 yr forego quality of life-enhancing surgery based largely on hypothesis-generating cohort studies and a post hoc ergo propter hoc fallacy dating to a 1955 report by Bedford in the Lancet, which suggested that persistent Postoperative Cognitive Decline was a concern following complaints from patients and their families regarding problems with cognitive function after surgery. . . . older patients should today be reassured that surgery and anesthesia are unlikely to be implicated in causing persistent cognitive decline or incident dementia.”

This editorial exposes the fallacy of post hoc ergo propter hoc, i.e. after this, therefore because of this, which has in the past led individuals to postulate that because a patient shows cognitive decline after surgery and anesthesia, that the cognitive decline must have been caused by surgery and anesthesia.

The authors of the editorial also admit that the first time detection of cognitive decline or dementia can be noted postoperatively for several reasons, including 1) cognitive decline or dementia are common in an aging population, approximately 50% of patients over the age of 60 undergo surgery, and the cognitive decline or dementia may first be detected at a time following surgery; 2) the preoperative trajectory of cognitive decline or dementia is rarely assessed, and postoperative cognitive decline or dementia is a continuation of the preoperative decline; 3) rapid onset cognitive decline or dementia can occur, and at times this decline will manifest and coincide with the time following surgery and anesthesia; and 4) it is difficult to change a firmly held conviction of past researchers, clinicians, and the general public that cognitive decline or dementia are caused by surgery and anesthesia.

The take home message is this: If you or one of your loved ones are over the age of 60 and need a surgical procedure to improve the quality of life, there should be no reluctance to have the surgery because of the fear of postoperative cognitive decline or dementia.


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Published in September 2017:  The second edition of THE DOCTOR AND MR. DYLAN, Dr. Novak’s debut novel, a medical-legal mystery which blends the science and practice of anesthesiology with unforgettable characters, a page-turning plot, and the legacy of Nobel Prize winner Bob Dylan.


In this debut thriller, tragedies strike an anesthesiologist as he tries to start a new life with his son.

Dr. Nico Antone, an anesthesiologist at Stanford University, is married to Alexandra, a high-powered real estate agent obsessed with money. Their son, Johnny, an 11th-grader with immense potential, struggles to get the grades he’ll need to attend an Ivy League college. After a screaming match with Alexandra, Nico moves himself and Johnny from Palo Alto, California, to his frozen childhood home of Hibbing, Minnesota. The move should help Johnny improve his grades and thus seem more attractive to universities, but Nico loves the freedom from his wife, too. Hibbing also happens to be the hometown of music icon Bob Dylan. Joining the hospital staff, Nico runs afoul of a grouchy nurse anesthetist calling himself Bobby Dylan, who plays Dylan songs twice a week in a bar called Heaven’s Door. As Nico and Johnny settle in, their lives turn around; they even start dating the gorgeous mother/daughter pair of Lena and Echo Johnson. However, when Johnny accidentally impregnates Echo, the lives of the Hibbing transplants start to implode. In true page-turner fashion, first-time novelist Novak gets started by killing soulless Alexandra, which accelerates the downfall of his underdog protagonist now accused of murder. Dialogue is pitch-perfect, and the insults hurled between Nico and his wife are as hilarious as they are hurtful: “Are you my husband, Nico? Or my dependent?” The author’s medical expertise proves central to the plot, and there are a few grisly moments, as when “dark blood percolated” from a patient’s nostrils “like coffee grounds.” Bob Dylan details add quirkiness to what might otherwise be a chilly revenge tale; we’re told, for instance, that Dylan taught “every singer with a less-than-perfect voice…how to sneer and twist off syllables.” Courtroom scenes toward the end crackle with energy, though one scene involving a snowmobile ties up a certain plot thread too neatly. By the end, Nico has rolled with a great many punches.

Nuanced characterization and crafty details help this debut soar.

Click on the image below to reach the Amazon link to The Doctor and Mr. Dylan:






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