Impact of bariatric surgery on cerebral vascular reactivity and cognitive function: a non-randomized pilot study

Bariatric Surgery Is Associated With Reduced Incidence of Mild Cognitive Impairment and Alzheimer Disease and Related Dementias: A Retrospective Cohort Study

Objective

To evaluate the association of bariatric surgery with reduced incidence and delayed development of mild cognitive impairment (MCI) and Alzheimer disease and related dementias (ADRD) in patients with obesity.

Background

This retrospective longitudinal study utilized Electronic Health Records from Vanderbilt University Medical Center, covering 5303 patients who underwent bariatric surgery and 10,606 propensity score-matched obese patients who did not, from 2000 to 2023. Patients with prior MCI, ADRD, schizophrenia, alcoholism, gastric cancer, gastric ulcers, inflammatory bowel disease, coagulopathy, stroke, Parkinson disease, or brain cancer were excluded from both groups.

Methods

Differences in time to MCI/ADRD between surgical and control groups were analyzed using linear regression, and adjusted for confounders: demographics, medical history, and socioeconomic status. Survival probability differences for MCI and ADRD between the 2 groups over time were assessed using Kaplan-Meier curves and log-rank tests. Incidence differences of MCI and ADRD between the groups were evaluated using Fine-Gray subdistribution hazard models, accounting for the competing risk of death and confounders.

Results

Bariatric surgery was associated with a significantly reduced incidence of ADRD, evidenced by a subdistribution hazard ratio (SHR) of 0.37 (95% confidence interval [CI]: 0.15-0.89; P = 0.03). Similarly, the incidence of MCI was significantly lower in the surgical group, with an SHR of 0.57 (95% CI: 0.39-0.85; P = 0.01). Additionally, patients who underwent bariatric surgery experienced a delay of 2.01 years before developing MCI compared with the control group (95% CI: 0.70-3.50; P = 0.004).

Conclusions

These findings suggest that bariatric surgery may serve as an effective strategy to delay the onset of MCI and reduce the risk of both MCI and ADRD in patients with obesity.

Changes in Cognitive Function Following Bariatric Surgery: An Updated Systematic Review

Since a previous systematic review published in 2016, there have been further studies investigating the association of changes in cognitive function following bariatric surgery. All studies since the original review that reported at least one element of cognitive function before and after bariatric surgery were eligible. A total of 137 additional studies were identified; 13 were included in addition to the 18 studies previously. Almost all studies reported improvements in at least one domain. Most revealed improvements were limited to a few domains and were not universal. Further findings investigated cognitive function improvement in relation to procedure choice, and mental health or quality of life post-surgery. Further high-powered studies are still necessary, but these findings support the impact of bariatric surgery on cognitive function in obesity.

Peripheral and Cerebral Vasodilation in Black and White Women: Examining the Impact of Psychosocial Stress Exposure Versus Internalization and Coping

BACKGROUND

Black women have among the highest rates of cardiovascular and cerebrovascular disease prevalence and mortality in part due to blunted vascular function. Psychosocial stress likely also contributes but its relationship to vascular function remains incompletely understood. Recent studies suggest that stress internalization and coping strategies are more important than stress exposures alone. We hypothesized that Black women would have blunted peripheral and cerebral vasodilation and that, among Black women, this would be inversely related with psychosocial stress internalization/coping but not stress exposures.

METHODS

Healthy Black (n=21; 20±2 years) and White (n=16; 25±7 years) women underwent testing for forearm reactive hyperemia, brachial artery flow-mediated dilation (FMD), and cerebrovascular reactivity. Psychosocial stress exposures (adverse childhood experiences; past week discrimination) and internalization/coping techniques (John Henryism Active Coping Scale; Giscombe Superwoman Schema Questionnaire) were assessed.

RESULTS

Reactive hyperemia and cerebrovascular reactivity were not different between groups (P>0.05), whereas FMD was lower in Black women (P=0.007). Neither adverse childhood experiences nor past week discrimination were associated with FMD in either group (P>0.05 for all). John Henryism Active Coping Scale scores were negatively associated with FMD in Black women (P=0.014) but positively associated with FMD in White women (P=0.042). Superwoman Schema-Succeed was negatively associated (P=0.044) and Superwoman Schema-Vulnerable tended to be negatively associated (P=0.057) with FMD in Black women.

CONCLUSIONS

These findings indicate that blunted FMD in Black women may be due more to stress internalization and maladaptive coping than stress exposures alone.

A Systematic Review of the Association Between Dementia Risk Factors and Cerebrovascular Reactivity

Cumulative evidence suggests that impaired cerebrovascular reactivity (CVR), a regulatory response critical for maintaining neuronal health, is amongst the earliest pathological changes in dementia. However, we know little about how CVR is affected by dementia risk, prior to disease onset. Understanding this relationship would improve our knowledge of disease pathways and help inform preventative interventions. This systematic review investigates 59 studies examining how CVR (measured by magnetic resonance imaging) is affected by modifiable, non-modifiable, and clinical risk factors for dementia. We report that non-modifiable risk (older age and apolipoprotein ε4), some modifiable factors (diabetes, traumatic brain injury, hypertension) and some clinical factors (stroke, carotid artery occlusion, stenosis) were consistently associated with reduced CVR. We also note a lack of conclusive evidence on how other behavioural factors such as physical inactivity, obesity, or depression, affect CVR. This review explores the biological mechanisms underpinning these brain- behaviour associations, highlights evident gaps in the literature, and identifies the risk factors that could be managed to preserve CVR in an effort to prevent dementia.

Peripheral and Cerebral Vascular Reactivity in Black and White Women: Examining the Impact of Psychosocial Stress Exposure Versus Internalization and Coping

Black women have the highest rates of cardiovascular and cerebrovascular disease prevalence and mortality in part due to blunted vascular function. Psychosocial stress likely also contributes but its relationship to vascular function remains incompletely understood. Recent studies suggest that internalization and coping strategies are more important than stress exposure alone. We hypothesized that Black women have blunted peripheral and cerebral vascular function and that, among Black women, this would be inversely related with psychosocial stress internalization/coping but not stress exposures. Healthy Black ( n = 21; 20 ± 2 yr) and White ( n = 16; 25 ± 7 yr) women underwent testing for forearm reactive hyperemia (RH), brachial artery flow-mediated dilation (FMD), and cerebrovascular reactivity (CVR). Psychosocial stress exposure (adverse childhood experiences, ACEs; past week discrimination, PWD) and internalization/coping techniques (John Henryism Active Coping Scale, JHAC12; Giscombe Superwoman Schema Questionnaire, G-SWS-Q) were assessed. RH and CVR ( p > 0.05) were not different between groups whereas FMD was lower in Black women ( p = 0.007). Neither ACEs nor PWD were associated with FMD in either group ( p > 0.05 for all). JHAC12 scores were negatively associated with FMD in Black women ( p = 0.014) but positively associated with FMD in White women ( p = 0.042). SWS-Succeed was negatively associated ( p = 0.044) and SWS-Vulnerable tended to be negatively associated ( p = 0.057) with FMD in Black women. These findings indicate that blunted FMD in Black women may be due more to internalization and maladaptive coping than stress exposure alone.

Brain effect of bariatric surgery in people with obesity

BACKGROUND/OBJECTIVES

The link between obesity and brain function is a fascinating but still an enigmatic topic. We evaluated the effect of Roux-en-Y gastric bypass (RYGB) on peripheral glucose metabolism, insulin sensitivity, brain glucose utilization and cognitive abilities in people with obesity.

SUBJECTS/METHODS

Thirteen subjects with obesity (F/M 11/2; age 44.4 ± 9.8 years; BMI 46.1 ± 4.9 kg/m²) underwent 75-g OGTT during a [18F]FDG dynamic brain PET/CT study at baseline and 6 months after RYGB. At the same timepoints, cognitive performance was tested with Mini Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Trail making test (TMT) and Token test (TT). Glucose, insulin, C-peptide, GLP-1, GIP, and VIP levels were measured during OGTT. Leptin and BDNF levels were measured before glucose ingestion.

RESULTS

RYGB resulted in significant weight loss (from 46.1 ± 4.9 to 35.3 ± 5.0 kg/m²; p < 0.01 vs baseline). Insulin sensitivity improved (disposition index: from 1.1 ± 0.2 to 2.9 ± 1.1; p = 0.02) and cerebral glucose metabolic rate (CMRg) declined in various brain areas (all p ≤ 0.01). MMSE and MoCA score significantly improved (p = 0.001 and p = 0.002, respectively). TMT and TT scores showed a slight improvement. A positive correlation was found between CMRg change and HOMA-IR change in the caudate nucleus (ρ = 0.65, p = 0.01). Fasting leptin decreased (from 80.4 ± 13.0 to 16.1 ± 2.4 ng/dl; p = 0.001) and correlated with CMRg change in the hippocampus (ρ = 0.50; p = 0.008). CMRg change was correlated with cognitive scores changes on the TMT and TT (all p = 0.04 or less).

CONCLUSIONS

Bariatric surgery improves CMRg directly related to a better cognitive testing result. This study highlights the potential pleiotropic effects of bariatric surgery.

TRIAL REGISTRY NUMBER

NCT03414333.

Cognition and brain oxygen metabolism improves after bariatric surgery-induced weight loss: A pilot study

OBJECTIVE

The primary objectives of this pilot study were to assess cognition and cerebral metabolic rate of oxygen (CMRO₂) consumption in people with severe obesity before (baseline), and again, 2- and 14-weeks after sleeve gastrectomy bariatric surgery.

METHODS

Six people with severe/class 3 obesity (52 ± 10 years, five females, body mass index (BMI) = 41.9 ± 3.9 kg/m²), and 10 normal weight sex- and age-matched healthy controls (HC) (48 ± 6 years, eight females, 22.8 ± 1.9 kg/m²). Global CMRO₂ was measured non-invasively using MRI and cognition using the Integneuro testing battery.

RESULTS

Following a sleeve gastrectomy induced weight loss of 6.4 ± 2.5 kg (% total-body-weight-lost = 5.4) over two-weeks, cognition total scores improved by 0.8 ± 0.5 T-scores (p=0.03, 15.8% improvement from baseline). Weight loss over 14-weeks post-surgery was 15.4 ± 3.6 kg (% total-body-weight-lost = 13.0%) and cognition improved by 1.1 ± 0.4 (p=0.003, 20.6% improvement from baseline). At 14-weeks, cognition was 6.4 ± 0.7, comparable to 6.0 ± 0.6 observed in the HC group. Baseline CMRO₂ was significantly higher compared to the HC (230.4 ± 32.9 vs. 177.9 ± 33.9 µmol O₂/100 g/min, p=0.02). Compared to baseline, CMRO₂ was 234.3 ± 16.2 µmol O₂/100 g/min at 2-weeks after surgery (p=0.8, 1.7% higher) and 217.3 ± 50.4 at 14-weeks (p=0.5, 5.7% lower) after surgery. 14-weeks following surgery, CMRO₂ was similar to HC (p=0.17).

CONCLUSION

Sleeve gastrectomy induced weight loss was associated with an increase in cognition and a decrease in CMRO₂ observed 14-weeks after surgery. The association between weight loss, improved cognition and CMRO₂ decrease should be evaluated in larger future studies.

Cerebrovascular Reactivity Measurement Using Magnetic Resonance Imaging: A Systematic Review

Cerebrovascular reactivity (CVR) magnetic resonance imaging (MRI) probes cerebral haemodynamic changes in response to a vasodilatory stimulus. CVR closely relates to the health of the vasculature and is therefore a key parameter for studying cerebrovascular diseases such as stroke, small vessel disease and dementias. MRI allows in vivo measurement of CVR but several different methods have been presented in the literature, differing in pulse sequence, hardware requirements, stimulus and image processing technique. We systematically reviewed publications measuring CVR using MRI up to June 2020, identifying 235 relevant papers. We summarised the acquisition methods, experimental parameters, hardware and CVR quantification approaches used, clinical populations investigated, and corresponding summary CVR measures. CVR was investigated in many pathologies such as steno-occlusive diseases, dementia and small vessel disease and is generally lower in patients than in healthy controls. Blood oxygen level dependent (BOLD) acquisitions with fixed inspired CO₂ gas or end-tidal CO₂ forcing stimulus are the most commonly used methods. General linear modelling of the MRI signal with end-tidal CO₂ as the regressor is the most frequently used method to compute CVR. Our survey of CVR measurement approaches and applications will help researchers to identify good practice and provide objective information to inform the development of future consensus recommendations.

Bariatric Surgery Induces Retinal Thickening Without Affecting the Retinal Nerve Fiber Layer Independent of Diabetic Status

PURPOSE

Obese patients have neurodegeneration of the optic nerve demonstrated by decreased peripapillary nerve fiber layer. Whether bariatric surgery reverses this neurodegenerative process has not been explored. We aimed to evaluate the impact of bariatric surgery in the structure of the retina and optic nerve.

METHODS

Multicentric observational study. Obese patients scheduled for bariatric surgery were consecutively recruited and included in the study and evaluated before and 6-12 months after the intervention. The retinal structure was evaluated as retinal thickness in the different retinal layers in the foveal, perifoveal, and parafoveal regions using optical coherence tomography. Choroidal thickness and optic nerve retinal nerve fiber layer thickness were also evaluated.

RESULTS

Eighty eyes from 40 participants were included. Globally, we found a significant thickening of the retina after bariatric surgery (foveal: 273.5 (21.5) μm vs 280.0 (28.8) μm, p < 0.001; parafoveal 332.4 ± 17.8 μm vs 336.6 ± 15.9 μm, p = 0.003; perifoveal: 293.4 ± 13.8 μm vs 295.7 ± 14.9 μm; p = 0.001), whereas no significant differences were found for the ganglion cell layer, choroid, or peripapillary nerve fiber layer thickness. The retinal thickening was confined to inner retinal layers and was independent of the diabetic status of the patients. After multivariate adjustment, HbA1c variation, preoperative C-peptide, preoperative hypertension, preoperative OSA, and preoperative LDL and TG levels seem to be clinical predictors of retinal thickening.

CONCLUSIONS

We found a significant thickening of the retina after bariatric surgery that was independent of the diabetic status. The thickening was confined to inner retinal layers and may represent and improve perfusion. The peripapillary nerve fiber layer remained unchanged after the surgery.