A University of Sydney-led study has linked multiple surgeries to small but cumulative declines in cognitive function among older adults.
Researchers analysed data from nearly 500,000 UK Biobank participants, aged 40-69, across two decades of brain imaging, cognitive tests and medical records.
The study found that each surgery contributed modestly to slower reaction times, diminished memory, and reduced problem-solving abilities, with physical changes observed in memory-related brain areas, such as a smaller hippocampus.
It is the first study to investigate the impact of multiple, complex surgeries on brain health using brain imaging techniques such as MRIs in a large population.
As part of the study, patients underwent brain MRIs and cognitive function testing for signs of neurodegeneration.
It found that, with each additional surgery, patients’ overall reaction time slowed by 0⋅3 milliseconds. Cognitive flexibility, problem-solving and picture and number recall decreased with each additional surgery.
People who had surgeries were also found to have a smaller hippocampus, the brain area responsible for memory and learning. They also had more evidence of brain damage associated with blocked blood vessels compared to those who did not undergo repeated surgeries.
Lead researcher Dr Jennifer Taylor, from the University of Sydney’s Faculty of Medicine and Health, said: ‘The results suggest that the cognitive decline per surgery may seem small, but those changes and losses in neurodegeneration start to add up after multiple surgeries. We found that surgeries are safe on average but also that the burden of numerous surgeries on the brain health of older patients should not be underestimated.
‘This is a reminder to medical professionals to consider all treatment options and be cautious in recommending major surgery for older and more vulnerable patients. If surgery is the best or only treatment option, patients should be reassured that the cognitive harm from each surgery is small on average. Nonetheless, careful attention in perioperative care is required to prioritise brain health and recovery.’
Published in The Lancet Healthy Longevity, the researchers examined the impact of surgical and medical hospital admissions on cognition, using a large population-based sample of British adults from the UK Biobank from 2006- 2023.
UK Biobank is the world’s most comprehensive source of health data available for research.
It houses a vast and continuously growing dataset of biological, health, and lifestyle information collected over 15 years from half a million UK volunteers.
Data was pooled from 46,706 people who underwent detailed magnetic resonance imaging (MRI) and cognition tests.
Participants were tested on their reaction time, memory, and ability to think flexibly by answering a series of language-of-mathematics questions.
This study continues work from the same research team that previously found major surgery (including cardiac, thoracic, vascular, and intracranial surgeries) and hospital admissions are associated with cognitive decline among older patients.
The researchers say future work should focus on understanding the biological inner workings of neurodegeneration. One hypothesis suggests inflammation could be the reason for delayed cognitive recovery after surgery, and understanding how this leads to brain damage will be a critical next step.
Senior author Professor Robert Sanders from the University of Sydney and Royal Prince Alfred Hospital said: ‘This paper represents a critical milestone for our field, defining the importance of research into perioperative brain health. We are already testing potential therapeutics in clinical trials as we strive to advance safe anaesthesia and perioperative care.
