Alzheimer's Dementia After Exposure to Anesthesia and Surgery in the Elderly: A Matched Natural Experiment Using Appendicitis

Association between surgery and rate of incident dementia in older adults: A population-based retrospective cohort study

BACKGROUND

The risk of incident dementia after surgery in older adults is unclear. The study objective was to examine the rate of incident dementia among older adults after elective surgery compared with a matched nonsurgical control group.

METHODS

We conducted a population-based, propensity-matched retrospective cohort study using data from linked administrative databases in Ontario, Canada. All community-dwelling individuals aged 66 years and older who underwent one of five major elective surgeries between April 1, 2007 and March 31, 2011 were included. Each surgical patient was matched 1:1 on surgical specialty of the surgeon at consultation, age, sex, fiscal year of entry, and propensity score with a patient who attended an outpatient visit with a surgeon of the same surgical specialty but did not undergo surgery. Patients were followed for up to 5 years after cohort entry for the occurrence of a new dementia diagnosis, defined from administrative data. Cause-specific hazard models were used to estimate the hazard ratio (HR) and 95% confidence interval (CI) for the association between surgery and the hazard of incident dementia. Subgroup and sensitivity analyses were performed.

RESULTS

A total of 27,878 individuals (13,939 matched pairs) were included in the analysis. A total of 640 (4.6%) individuals in the surgical group and 965 (6.9%) individuals in the control group developed dementia over the 5-year follow-up period. Individuals who underwent surgery had a reduced rate of incident dementia compared with their matched nonsurgical controls (HR 0.88; 95% CI 0.80-0.97; p = 0.01). This association was persistent in most subgroups and after sensitivity analyses.

CONCLUSIONS

Elective surgery did not increase the rate of incident dementia when compared with matched nonsurgical controls. This could be an important consideration for patients and surgeons when elective surgery is considered.

Behavioural disorders after prenatal exposure to anaesthesia for maternal surgery

BACKGROUND

The association between prenatal exposure to general anaesthesia for maternal surgery during pregnancy and subsequent risk of disruptive or internalising behavioural disorder diagnosis in the child has not been well-defined.

METHODS

A nationwide sample of pregnant women linked to their liveborn infants was evaluated using the Medicaid Analytic eXtract (MAX, 1999-2013). Multivariate matching was used to match each child prenatally exposed to general anaesthesia owing to maternal appendectomy or cholecystectomy during pregnancy with five unexposed children. The primary outcome was diagnosis of a disruptive or internalising behavioural disorder in children. Secondary outcomes included diagnoses for a range of other neuropsychiatric disorders.

RESULTS

We matched 34,271 prenatally exposed children with 171,355 unexposed children in the database. Prenatally exposed children were more likely than unexposed children to receive a diagnosis of a disruptive or internalising behavioural disorder (hazard ratio [HR], 1.31; 95% confidence interval [CI], 1.23-1.40). For secondary outcomes, increased hazards of disruptive (HR, 1.32; 95% CI, 1.24-1.41) and internalising (HR, 1.36; 95% CI, 1.20-1.53) behavioural disorders were identified, and also increased hazards of attention-deficit/hyperactivity disorder (HR, 1.32; 95% CI, 1.22-1.43), behavioural disorders (HR, 1.28; 95% CI, 1.14-1.42), developmental speech or language disorders (HR, 1.16; 95% CI, 1.05-1.28), and autism (HR, 1.31; 95% CI, 1.05-1.64).

CONCLUSIONS

Prenatal exposure to general anaesthesia is associated with a 31% increased risk for a subsequent diagnosis of a disruptive or internalising behavioural disorder in children. Caution is advised when making any clinical decisions regarding care of pregnant women, as avoidance of necessary surgery during pregnancy can have detrimental effects on mothers and their children.

Stress Granules Modulate SYK to Cause Tau-Associated Neurocognitive Deterioration in 5XFAD Mouse After Anesthesia and Surgery

Background

Alzheimer’s disease (AD) is the most common type of dementia. However, no curative therapy has been found effective to slow down the process of AD. It is reported that anesthesia and surgery will induce neurocognitive deterioration in AD, but the mechanism is not quite clear. In this study, we aim to compare the cognitive impairment between 5XFAD transgenic (Tg) mice and its littermate (LM) after isoflurane anesthesia and surgery to clarify the specific impacts of anesthesia and surgery on individuals with AD and to explore the mechanisms.

Methods

We performed abdominal surgery in cognitively impaired, 4-month-old female 5XFAD mice and LM control mice. Isoflurane anesthesia (1.4%) was induced and maintained over 2 h. Open field and fear conditioning tests were conducted on 1, 3 and 7 days after anesthesia and surgery. The total distance, velocity and freezing time were the major outcomes. P-tau (AT8), tau oligomers (T22), stress granules (SGs), the SYK tyrosine kinase and p-SYK in the hippocampus at postoperative day 1 were evaluated by Western Blot assays. The colocalization of SGs, SYK, p-SYK, and neurons in the hippocampus section was assessed using qualitative immunofluorescence.

Results

In the open field test, no difference between the distance moved and the velocity of LM mice and 5XFAD Tg mice were found on day 1 after anesthesia and surgery. 5XFAD Tg mice exhibited reduced freezing time of fear conditioning context test on postoperative day 3, but not on day 7; the LM mice showed no changes in FCTs. Furthermore, p-tau, tau oligomers, SGs, SYK and p-SYK were evident in the hippocampus region of 5XFAD Tg mice on a postoperative day 1. In addition, SGs, SYK, p-SYK were colocalized with hippocampus neurons, as shown by immunofluorescence.

Conclusion

This study demonstrates that anesthesia and surgery may induce tau-associated neurocognitive deterioration in individuals with AD. The mechanism under it may be associated with SGs and the tyrosine kinase, SYK. After anesthesia and surgery, in 5XFAD Tg mice, SGs were formed and SYK was phosphorylated, which may contribute to the phosphorylation of tau protein. This study provided hints that individuals with AD may be more vulnerable to anesthesia and surgery.