It’s been a major concern for the last 60 years.

But as yet, we still don’t know whether surgery harms the brain. And I’m not just talking about brain operations – I mean any kind of surgery. Most of the concern focuses on anesthesia and its effects.

Previous studies have been inconsistent. Some report negative changes; others suggest no effect; one even showed an improvement in cognition.

I thought it was time to try to dig up some reliable evidence. . .

Surgery Doubles Risk of Substantial Cognitive Decline

A survey carried out by Dr. Robert Sanders and his colleagues at the University of Wisconsin, Madison, found two out of every three members of the public were concerned that surgery could harm their memories.

These findings worried the researchers.

It could lead people to skip medical interventions that could provide a better quality of life because they fear for their cognitive functions.

So to see if this fear is based in reality, Dr. Sanders and his team assessed health data from Whitehall II, a study of 7,532 British civil servants who have been followed for the last 30 years. Participants were aged 35 to 55 at the start of the study and received a regular battery of cognitive tests over most of this period.

After taking into account the expected decline in cognition that comes with aging, the researchers found that major surgery – defined as needing at least a two-night hospital stay – was linked to a small additional decline in cognition equivalent to around five months of aging over the long term.

But get this: The surgery patients were apparently better off compared to those hospitalized for at least two nights for conditions that didn’t require surgery. These added 1.4 years of aging. This soared to 13 years for stroke patients.

However, a small number of surgical patients did suffer substantial cognitive decline.

For participants in the study who were never hospitalized, the chances of experiencing a large decline in reasoning, memory and language skills occurred in a small number — 2.5% — but this rose to 5.5% for those who had surgery, or as the study authors put it, “the risk of a large cognitive ‘hit’ is about doubled…”

Again, this proved less of a risk than for non-surgical medical admission where the percentage soared to 12.7.

A Bigger Concern – Non-Surgical Admission

Dr. Sanders commented on the findings:

“Earlier work has shown that a large share of the population fears that surgery may produce cognitive decline. Our analysis reveals a small degree of risk compared to not being admitted, but substantially less than that associated with hospital admissions without surgery.

“Since this is an observational study, we cannot identify surgery as the cause of the small change in cognition. Needing surgery is associated with differences in health that might itself cause cognitive changes, and subjects should weigh the small risk of cognitive decline against the potential health benefits of surgery.”

If surgery does provoke brain injury, Dr. Sanders suggested this could come about through mini-strokes and inflammation experienced during the procedure, while the effect on long term brain function could be influenced by post-operative pain and some medications.

Since the study was concerned with surgery, no details were provided concerning non-surgical admissions (apart from stroke), so we don’t know why these patients were admitted or how long they stayed in hospital compared to surgical patients.

What Does It All Mean?

My take on all this is that it’s hard to know what to make of these findings. I’m encouraged to see that surgery does NOT seem to give rise to a huge increase in dementia risk for most patients (at least among British civil servants!)

But I’m concerned that the study found double the risk of large cognitive decline compared to people who had never been in a hospital. Admittedly, only a small percentage of surgical patients saw this catastrophic loss of memory in later years, but for them it looks like it might have been averted if somehow they had been able to avoid surgery.

The really bad news, on the other hand, is for the folks who were hospitalized but did not undergo surgery. For them, the news is dire.

The researchers wrote that non-stroke medical admissions were associated with a “four-fold larger cognitive effect than major surgery.”

I’m puzzled as to why a hospital stay for nonsurgical reasons is linked to such a leap in dementia risk.  There are so many possible reasons for these hospital admissions – pneumonia, concussion, heart attack, you name it – it’s hard to say what to make of this study.

Hospitals are dangerous places at the best of times; this study reinforces the need to do everything we can to stay in good shape to reduce the chances of ending up in hospital in the first place.


  1. https://www.bmj.com/content/366/bmj.l4466
  2. https://news.wisc.edu/uw-study-major-surgery-is-associated-with-minor-cognitive-decline/

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