Alzheimer's disease Brain Featured Mental health The Memory Doctor

Does surgery cause or worsen dementia?

Question: My father needs surgery. Will this worsen his dementia?

Answer: This is one of the more common questions I get asked as a dementia specialist. Similarly, there are numerous families that come to me on the first visit, convinced that their relative’s dementia started immediately after some type of surgery. So, does surgery cause or worsen dementia?

There have been numerous studies over the years that have attempted to answer this question. Unfortunately, the results are often conflicting, with some studies showing an increased risk of dementia and/or cognitive impairment (a decline in memory and thinking skills) following surgery, and others suggesting no increase risk. As you might imagine, the reasons for these discrepancies are that the results likely depend on a multitude of factors including the characteristics of the patients (age, medical conditions, medications, pre-existing cognitive impairment), the type of condition requiring surgery (including emergency or elective), the type of surgery, the anaesthetic (general or local) and the operative complications (e.g. blood loss or infection).

With these conflicting results in mind, there are many reasons to be concerned about the potential effects of surgery on cognition. Surgical procedures generally lead to inflammation and immunological responses that can negatively affect the brain. During surgery, blood flow to the brain may be impaired because of changing fluid levels or blood loss. Some surgical procedures might directly increase the risks of small strokes. Some anaesthetic drugs have potential to impair memory and cognitive function. Following surgery, pain and medications used to treat pain and other operative complications could impair cognition.

Perhaps the greatest threat to cognition is the common post-operative complication of delirium. Delirium is an acute confusional state where the patient will appear disoriented, unable to focus or concentrate, present with severe memory problems and might have a variety of emotional issues including hallucinations, paranoia, anxiety, agitation and depression. These symptoms appear suddenly after surgery and can wax and wane over several days. The risk factors for post-operative delirium include greater age and pre-existing cognitive impairment (and dementia). Delirium is associated with greater lengths of hospital stay, increased risk of institutionalization and death. While cognition often improves after delirium resolves, delirium is also associated with worsening of pre-existing cognitive impairment and dementia. Treating and preventing post-operative delirium is therefore crucial.

Unfortunately, surgery is often unavoidable, and in those instances, patients and caregivers may have very little choice in whether to proceed or not. In cases where the proposed surgery is more elective, patients and families will need the assistance of their physicians to evaluate the relative risks and benefits of proceeding with the operation. In all cases, making sure the surgeon and the anaesthesiologist are aware of pre-existing cognitive impairment or dementia are essential. This knowledge will help guide the choice of anaesthesia and allow the team to monitor for post-operative delirium and treat as aggressively as possible in an attempt to limit poor cognitive and functional outcomes.

The story of surgery and dementia is not all negative. In a future blog, I will highlight some surgical procedures that might actually improve cognition and examine new ways that might specifically help protect the brain during operations.

About the author

Dr. Nathan Herrmann

Dr. Nathan Herrmann is an affiliate researcher/scientist with Sunnybrook. For 25 years Dr. Hermann has been a memory disorders specialist. He has done research in the fields of mental health in the aging, including dementia, Alzheimer’s disease, depression, and suicide. Read his blog series: The Memory Doctor.