Surgery, Anesthesia, and Risk for the Development of Dementia

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Velkers, Clive
Epidemiology , Dementia , Alzheimer's disease , Anesthesia , Geriatrics , Surgery
As Canadians continue to live longer, more older adults are undergoing surgical procedures. These procedures can leave patients at an increased risk for medical complications, and there has been growing interest in a potential association between surgery and dementia. When further examining this relationship, attention has been given to the potential role that anesthesia may have on risk for development of dementia. There are two main types of anesthesia administered for many surgeries, general (GA) and regional (RA). This thesis explored the association between surgery, anesthesia, and dementia by comparing for potential differences between GA and RA on the development of dementia following surgery. Using a retrospective cohort study design, older adults aged 66 years and greater who underwent elective surgical procedures were followed-up for up to 5 years following their index surgery. The surgical procedures that were included in this thesis were hip replacement, knee replacement, inguinal hernia repair, hysterectomy, and prostatectomy, since each are common procedures and can be completed using either GA or RA. Statistical analyses consisted of Kaplan-Meier survival curves and Cox proportional hazards models, where the hypothesis was that GA would lead to greater risk for the development of dementia following surgery compared to RA. To control for any potential differences in baseline characteristics that may bias the associations of interest and the outcome of dementia, matching was done on age, sex, index year, surgery, and propensity score. The final matched sample consisted of 14,998 individuals. A total of 725 people developed dementia throughout follow-up, 362 who received GA and 363 who received RA. After comparing people administered GA to those receiving RA, there was no significant difference in risk for development of dementia following surgery (HR = 1.0, 95% CI: 0.8 – 1.2, p = 0.9). Subgroup and sensitivity analyses supported these results, with no significant differences found between anesthesia groups. Therefore, this thesis found that there was no significant difference in dementia development following surgery when comparing people receiving GA and RA. Future studies should consider a randomized trial design and access more detailed data on the depth and duration of the anesthesia exposure.
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