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Risk of dementia after anaesthesia and surgery

  • Pin-Liang Chen (a1), Chih-Wen Yang (a2), Yi-Kuan Tseng (a3), Wei-Zen Sun (a4), Jane-Ling Wang (a5), Shuu-Jiun Wang (a6), Yen-Jen Oyang (a7) and Jong-Ling Fuh (a8)...

The potential relationship between anaesthesia, surgery and onset of dementia remains elusive.


To determine whether the risk of dementia increases after surgery with anaesthesia, and to evaluate possible associations among age, mode of anaesthesia, type of surgery and risk of dementia.


The study cohort comprised patients aged 50 years and older who were anaesthetised for the first time since 1995 between 1 January 2004 and 31 December 2007, and a control group of randomly selected patients matched for age and gender. Patients were followed until 31 December 2010 to identify the emergence of dementia.


Relative to the control group, patients who underwent anaesthesia and surgery exhibited an increased risk of dementia (hazard ratio = 1.99) and a reduced mean interval to dementia diagnosis. The risk of dementia increased in patients who received intravenous or intramuscular anaesthesia, regional anaesthesia and general anaesthesia.


The results of our nationwide, population-based study suggest that patients who undergo anaesthesia and surgery may be at increased risk of dementia.

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Corresponding author
Jong-Ling Fuh, Neurological Institute, Taipei Veterans General Hospital, Taipei, Taiwan. Email:
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These authors contributed equally to this work.

The study was supported by grants from Taipei Veterans General Hospital (V101C-105, VGHUST101-G7-1-2), National Science Council support for the Centre for Dynamical Biomarkers and Translational Medicine, National Central University, Taiwan (NSC 100-2911-I-008-001), support from the Brain Research Centre at National Yang-Ming University and a grant from the Taiwanese Ministry of Education's Aim for the Top university plan. J.L.W.'s work was supported, in part, by a National Institutes of Health grant (R01AG025218-01).

Declaration of interest


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Risk of dementia after anaesthesia and surgery

  • Pin-Liang Chen (a1), Chih-Wen Yang (a2), Yi-Kuan Tseng (a3), Wei-Zen Sun (a4), Jane-Ling Wang (a5), Shuu-Jiun Wang (a6), Yen-Jen Oyang (a7) and Jong-Ling Fuh (a8)...
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Risk of dementia after aneathesia and surgery: difficulties in proving causality

Adnan Sharaf, CT2 in Psychiatry
18 May 2014

Dear Sir,I read with interest the study by Chen et al11. They should be congratulated on further researching this potential link and thus continuing to raise the profile of dementia. I believe that this is an exceptionally difficult field to study and indeed they have raised some important points when discussing the limitations of the study. However they have failed to address what I feel is a vital question which needs tobe asked when addressing a study of this nature. Namely What is Anaesthesia? Clearly any standard textbook can discuss the triad of anaesthesia but if we are to investigate a causal link between anaesthesiaand a condition, we must first ask ourselves are we investigating the administration of potential neurotoxic drugs? Or are we investigating theartificial manipulation of physiology inherent in anaesthesia? If we are to consider the concept of the drugs alone then the wide variability of induction doses and maintenance doses must be considered. We must also consider the grade and skill of the individual anaesthetist as well as their personal thresholds for manipulating changes in physiological parameters and personal threshold for depth of anaesthesia.

It is the individual heterogeneity in the practice of anaesthesia which will make it very difficult to study such causal links. Potential prospective trials would be plagued by problems regarding individual dosage for individual patients and standardisation of doses and physiologywould be impossible. I thus welcome the work done by Chen et al but feel the findings should be interpreted with caution.

1. Chen P, Yang C, Tseng, Y, Sun W,Wang J, Wang S, Oyang Y, Fuh J. Risk of dementia after anaesthesia and surgery. B J Psych. 2013; 1-6. doi:10.1192/bjp.bp. 112.119610

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Conflict of interest: None declared

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Risk of dementia after anaesthesia and surgery

Manjeet S. Bhatia
07 March 2014

The study Pin-Liang Chen is an excellent long term study to study theassociation of dementia with anaesthesia and surgery, but the study needs cautious interpretation due to many shortcoming. Firstly, the other many important variables of anaesthesia (type and dose of agent used, duration of anaesthesia, other pre-anaesthetic agents used, anoxic episodes during surgery,post-anaesthetic outcome) and surgical variables (age-group, gender, indication and complications of surgery, co-morbid medical condition especially respiratory functions, diabetes, hypertension, dyslipidemia etc). Secondly, whether it was a first or repeated surgery (as many agents are cumulative). Thirdly, the branch of surgery (neurosurgery/cardiothoracic) or a routine surgery.Fouthly, the presence of co-morbid psychiatric disorder (depression,substance use especially alcohol, nicotine). Lastly, the history of head injury, seizure disorder or stroke will influence the risk of dementia. The study would have been more influential if surgical variables were controlled. But inspite of limitations, the study has opened an important area of research.

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