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 Table of Contents  
Year : 2022  |  Volume : 1  |  Issue : 2  |  Page : 82-87

Cognitive improvement following sleeve gastrectomy and roux-En-Y gastric bypass procedures

1 Department of Surgical Disciplines, AIIMS, New Delhi, India
2 Department of Neuropsychology, Neurosciences Centre, AIIMS, New Delhi, India
3 Department of Biostatistics, AIIMS, New Delhi, India

Date of Submission14-May-2022
Date of Acceptance06-Jul-2022
Date of Web Publication02-Aug-2022

Correspondence Address:
Dr. Sandeep Aggarwal
Department of Surgical Disciplines, All India Institute of Medical Sciences, Ansari Nagar, New Delhi
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/jbs.jbs_6_22

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Introduction: South Asia has noted an increasing prevalence of obesity and employment of bariatric surgery (BS) procedures. Prior studies have shown improvement in memory, executive function and attention, after Roux-en-Y gastric bypass (RYGB) operation in the Western population. However, there is a scarcity of data on cognitive improvement following BS in a non-Western population. Objective: The objective of the study is to evaluate changes in cognitive functions of patients with severe obesity, after BS. Study Setting: Tertiary-care Academic Center, India. Methodology: A prospective study of patients undergoing BS was conducted. Specific neurocognitive tests (Mini-mental Status Examination, Standard progressive matrices, Controlled Oral Word Association Test, and Post Graduate Institute Memory Scale test) were used to assess cognitive status at baseline (preoperatively), and at 3, 6, and 12 months. Results: Fifty-three patients were enrolled in the study, out of which 50 had completed 1 year of follow-up at the time of analysis (n = 50). Thirty-six patients (72%) were females. The median age was 42 years, and the mean preoperative body mass index (BMI) was 45.5 ± 6.3 kg/m2. 40 patients underwent SG, while 10 underwent RYGB procedure. At baseline, the study cohort had impairment of abstract reasoning, attention, and verbal retention, as compared to normative data. At 1 year after surgery, the mean BMI was 29.1 ± 2.6 kg/m2. There was a significant (P < 0.05) improvement in most cognitive domains (global cognitive functioning, abstract reasoning, attention/concentration, and memory function). However, improvement in language function was not found to be significant across the follow-up duration of 12 months (P = 0.35). Conclusions: Individuals with severe obesity experience baseline impairment in cognitive functions. Similar to results from the Western population, BS (RYGB and SG) results in a significant improvement in multiple cognitive domains even in a non-Western population.

Keywords: Asia, attention, bariatric surgery, cognition, executive function, India, memory, roux-en-Y gastric bypass, sleeve gastrectomy

How to cite this article:
Gurnani N, Gupta M, Aggarwal S, Nehra A, Sreenivas V. Cognitive improvement following sleeve gastrectomy and roux-En-Y gastric bypass procedures. J Bariatr Surg 2022;1:82-7

How to cite this URL:
Gurnani N, Gupta M, Aggarwal S, Nehra A, Sreenivas V. Cognitive improvement following sleeve gastrectomy and roux-En-Y gastric bypass procedures. J Bariatr Surg [serial online] 2022 [cited 2023 Feb 5];1:82-7. Available from: http://www.jbsonline.org/text.asp?2022/1/2/82/353188

  Introduction Top

Individuals with obesity may exhibit cognitive dysfunction. This is particularly prevalent in candidates for bariatric surgery (BS), with up to 18%–24% of such individuals demonstrating clinically meaningful levels of impairment on neuropsychological testing (executive function/memory function).[1] While cognition includes various domains such as memory, attention, executive functioning (pattern recognition, decision-making, and problem-solving), and language and perception; deficits in individuals with obesity are most commonly found to occur in the domains of memory and executive functioning.[2],[3] Consequently, these changes influence not only the postoperative weight loss noted by BS candidates but also their quality of life.[4],[5]

The previous decade witnessed multiple studies analyzing cognitive changes following Roux-en-Y gastric bypass (RYGB) procedure.[6],[7],[8],[9] Seminal works evaluating the Longitudinal Assessment of BS cohort for cognitive changes reported a significant improvement in domains of memory and executive functioning over 36-month following RYGB procedure.[7],[8] Currently, much of the published literature has analyzed cognitive changes following BS in the Western population. On the contrary, South Asia (including India) is experiencing some of the fastest-growing obesity rates worldwide[10],[11] and consequently, has also seen a rapid rise in the prevalence of BS. However, there exist no reports analyzing cognitive changes following BS in South Asia. The current study was thus planned as an extension to the existing literature, with an aim to evaluate a non-Western population for cognitive changes following BS.

  Methodology Top

This was a prospective study involving patients undergoing BS at our tertiary care teaching hospital. The inclusion criteria included individuals with body mass index (BMI) >37.5 kg/m2, or with BMI >32.5 kg/m2 in the presence of obesity-related comorbidities.[12],[13] Individuals who suffered from any major neuropsychiatric illness (major depression, psychosis, or anxiety disorders), or were receiving drugs with neurological side effects, or were visually or auditorily impaired were excluded from our study sample. Ethical clearance was obtained from the Institute Ethics Committee (Ref. No.: IESC/T-455). Each patient underwent a baseline preoperative testing and repeat neuropsychological assessment at 3, 6, and 12 months after surgery.

All BS procedures were performed by a single surgeon, using standard operative techniques. For SG, the greater curvature of the stomach was freed up till the cardioesophageal junction close to the stomach, with the use of a vessel-sealing device (Harmonic Scalpel, or LigaSure,) sparing the gastroepiploic vessels. The stomach was then resected with a linear stapler parallel to a 36F orogastric tube placed along the lesser curve, starting from 4 to 5 cm proximal to the pylorus. For RYGB, a window was created at the level of second gastric vessel and a 4–5 cm proximal gastric pouch was created. Antecolic Roux limb of proximal jejunum 70 cm distal to the ligament of Treitz was brought up and anastomosed to the pouch. Gastrojejunostomy was performed using a 45 mm stapler. The length of the Roux limb was measured, and the small bowel was transected at 130 cm and entero-enterotomy was done using a 60 mm linear stapler. Mesenteric defect and Petersen's defect were routinely closed in all patients.

Assessment of cognitive function

After eliciting a brief history, each participant was administered a battery of neurocognitive tests by a single psychologist, that included the Mini-Mental Status Examination Score (MMSE Score),[14] Standard Progressive Matrices (SPM),[15] Controlled Oral Word Association Test (COWA),[16] and Post Graduate Institute Memory Scale Tests (PGI MS).[17] The MMSE score was used to assess global cognitive function, the SPM test was used to assess abstract reasoning (executive function) and the COWA test was used to assess verbal fluency (language function) in the study population. PGI MS was used to assess the remaining domains (attention and concentration and memory function) by administering a particular visual or verbal cue, and requesting the candidates to reproduce the cue in the required format (by speaking/drawing/selecting). For each of these tests [Table 1], individuals were scored according to the testing guidelines; and scores were analyzed against the original normative data of the tests (based on healthy, nonobese population). The various neuropsychological tests were sourced from the department of clinical neuropsychology of our institute.
Table 1: Neuropsychological tests used for cognitive assessment

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Data were analyzed using SPSS software version 21 (IBM Corp. Released 2012. IBM SPSS Statistics for Windows, Version 21.0. Armonk, NY, USA: IBM Corp.). Continuous variables were described as means and standard deviations. Repeated measures ANOVA was applied to determine changes in weight, cognitive, and vitamin parameters. Pair-wise analysis of preoperative status, with the scores at 1 year of follow-up was undertaken. To determine the resolution of comorbidities, generalized estimation equations were employed using STATA 11 software. A P < 0.05 was considered statistically significant.

  Results Top

A total of 53 patients agreed to participate and were initially included in the study. Three patients were lost to follow-up and were excluded from the final analysis. At the time of analysis, 50 patients had completed 1 year of follow-up. Of these 50 patients, 36 (72%) were female. The median age was 42 years (range 18–61 years), and the mean preoperative BMI was 45.5 kg/m2 ± 6.3 kg/m2. Forty patients underwent sleeve gastrectomy (SG), and 10 underwent RYGB procedure.

Preoperatively, the cognitive functions were evaluated against the normative data by converting the results into age, sex, and education matched t-scores, with T-score < −1 indicating significant impairment. The mean baseline verbal fluency, delayed recall, immediate recall, visual retention, and recognition were within the normal range. However, scores of tests on attention and concentration, verbal retention, and abstract reasoning were found to be below the normal range [Table 2].
Table 2: Baseline cognitive scores of the study cohort (n=50)

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At 12 months' postoperatively, the mean BMI had decreased to 29.1 kg/m2 ± 2.6 kg/m2 (P < 0.001, excess weight loss = 65.5%). Global cognitive function, assessed using the MMSE test, yielded a mean baseline score of 27. This score increased progressively to 28.5 at the end of 12 months, with significant improvement (P < 0.01) for all pair-wise comparisons between different time points. Abstract reasoning also showed a significant improvement in the SPM score; from 83.9 points preoperatively to 95 points at 12 months of follow-up, with P < 0.01 for all pair-wise comparisons. Language function was assessed based on the average number of new words generated average new words. It was seen that the average number of new words increased from 7.2 preoperatively, to 8.1 at 12 months. However, unlike with other domains, a steady improvement in verbal fluency score was not observed, with the score reaching a maximum of 9.4 at 3 months, and then decreasing to 8.1 at 12 months.

For each of the seven tests administered as a part of the PGI MS test, a significant progressive increase was observed between the mean scores before surgery, and the scores at 3, 6, and 12 months of follow-up (P < 0.01 for all pairwise comparisons, except for improvement in recognition score between 6 months and 12 months, which had a P = 0.09). The results of various neurocognitive tests are given in [Table 3].
Table 3: Comparison of cognitive scores at preoperative assessment and at each follow-up time point

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  Discussion Top

The current study showed that severe obesity is associated with impairment in abstract reasoning, attention and concentration, and verbal retention; and a significant improvement in multiple cognitive domains is noted within 1 year of BS. Our study population had a preserved preoperative global cognitive functioning as per the MMSE test. This was not surprising, as the MMSE is not a very sensitive tool for the detection of mild cognitive impairment.[18] Thus, even though specific tests structured for detailed cognitive analysis show impairment in certain domains, MMSE might report a grossly intact cognitive status. The observed improvement of our cohort in domains of executive function, attention and concentration, and memory function following BS is in agreement with the previously published literature,[6],[7],[19] and extends our understanding by showing that an SG – predominant study cohort also experiences cognitive changes similar to those noted by studies evaluating the RYGB procedure.

Multiple reasons have been proposed to explain the cognitive improvement seen following BS, that include (but are not likely limited to): metabolic changes, reduced inflammation, alterations in levels of leptin/ghrelin, changes involving hypoperfused areas of the brain, and changes in the gut microbiome.[20],[21],[22],[23],[24] Increased Glucagon-like peptide-1 (GLP-1) status has been reported to be associated with a beneficial impact on the brain through a reduction in the number of β amyloid plaques that get accumulated secondary to insulin resistance, and subsequently, a reduction in inflammation of the neuronal tissue.[25] In addition, some studies have also suggested the resolution of obesity-related comorbidities (e.g., high blood pressure) as a cause of improvement in neurocognition through decrease in arterial stiffness and improvement in cerebral perfusion pressures.[26] Unlike the remaining domains, language function has not been shown to improve significantly, following BS.[7],[27],[28] Although we observed a slight increase in scores of language function (measured in terms of verbal fluency), the direction of change fluctuated across the duration of follow-up, and thus may not be suggestive of a definite improvement in verbal fluency. Neuroimaging studies in patients with obesity have linked obesity to cerebral hypoperfusion in areas of executive function, leading to frontal lobe dysfunction that may get reversed following significant weight loss.[29] Functional magnetic resonance imaging results, however, have shown language function to be localized to parietal and temporal areas, while weight loss is associated with an increase in frontal lobe perfusion. Moreover, language development, communication abilities and oral fluency come under the domain of crystallized intelligence, which is a relatively stable component of the cognitive functioning of an adult brain.[30] These might be the reasons to why a steady improvement of language function was not found in our study.

Our study cohort was predominantly an SG undergoing cohort (n = 40/50). Despite the rapid rise of SG as the preferred BS worldwide,[31] much of the existing literature has evaluated only RYGB procedure for postoperative cognitive changes.[6] The only prior report analyzing cognitive changes following SG was a 2020 study (Smith et al.) comparing outcomes in 18 candidates undergoing SG to 18 candidates undergoing RYGB.[19] At 3 months' postoperatively, the authors reported significant improvement in psychomotor speed and executive functioning for both the procedures but did not find a significant improvement in attention or memory function for patients undergoing SG. The similarities between cognitive changes (in certain domains) after SG and RYGB may be attributable to the similar impact of the two surgeries on inflammatory processes and metabolic status of the patients.[32],[33] However, RYGB is known to cause greater changes in postprandial GLP-1 than SG.[34] It is also associated with a delayed increase in ghrelin levels, while SG causes a sustained decrease in ghrelin due to the removal of the gastric fundus.[35] These hormonal differences may translate into a differential impact of the two surgeries on neurogenesis and cognitive functioning postoperatively. It is noteworthy that the follow-up by Smith et al. was too short to conclusively establish cognitive changes that may follow SG. Our study showed a persistent improvement (over 12 months) in all cognitive domains, except in language function; however, a head-on comparison of outcomes following the two procedures (SG and RYGB) could not be done here.

Cognitive impairment in patients with severe obesity can have wide-ranging implications. Deficits in higher-order cognitive abilities, such as inhibition, organization, planning, complex focus, and in memory, could lead to behavioral disinhibition and poor adherence to postoperative lifestyle changes.[36] As a result, individuals with severe obesity would have difficulty resisting temptation toward unhealthy food items and would have difficulty following the advised postoperative dietary changes. Spitznagel et al.[4] showed that both, executive function and memory, influence BMI at 12 months with correlation coefficients (R2) of 0.04 and 0.05, respectively. An increase in cognitive difficulties has been noted to be an independent contributor to poorer total and work-related QoL (R2 = 0.14, P = 0.04).[5] Hence, a better knowledge of cognitive changes following BS would add to our understanding of the multitude of benefits that can be imparted to patients with severe obesity.

We acknowledge that practice effects resulting from administering the same set of tests at each follow-up visit, cannot be ruled out as a confounding factor for the observations. However, certain factors argue against the possibility of our results being entirely due to these practice effects. First, multiple prior works have compared cognitive changes following BS, and have shown definitive improvement following BS, in comparison to control groups.[1],[9] In addition, a detailed evaluation of practice effects for repetitive neuropsychological assessments has shown that their extent varies across different cognitive functions; with some domains showing linear trends across different follow-up visits, and others showing nonlinear, or even, non-significant trends.[37] Thus, an observation of global cognitive improvement, involving multiple domains, is less likely to have been caused entirely due to practice effects. In addition, patients enrolled in our study group were exposed to the neurocognitive tests only once every 3 months, with no exposure in the interval periods.

Strengths and limitations

The strength of our study is that this is a prospective study that objectively assesses the impact of BS on a non-Western population, with change in cognitive domains as the primary endpoint. We observed a good follow-up rate, with 50 out of 53 patients completing 1 year of assessment. All patients were operated according to standard procedural guidelines, and by a single surgeon. The cognitive functions have been evaluated using standardized neurocognitive tests. In addition, while most studies that have analyzed cognitive changes included patients undergoing RYGB procedure, 80% of our patients underwent SG. Our study also had a few limitations. While this work does indicate the possibility of a multi-faceted improvement in cognitive functions after SG; further research, with a longer duration of follow-up, is necessary for a more conclusive evidence on the extent and maintenance of these benefits. Moreover, an objective correlation between the amount of weight loss and improvement in cognitive functioning scores was not carried out in the current work and should be considered in future studies on this topic. Furthermore, post-BS, patients are advised strict lifestyle modifications, such as increased physical activity, involvement in social support groups, and regular micronutrient supplementation. Such interventions may have had a positive impact on the mental health and cognitive status of our patients, that could have been a confounder for our study results.[38]

  Conclusions Top

We conclude that individuals with severe obesity experience impairment in certain cognitive domains. Similar to results from the Western population, BS (RYGB and SG) results in a significant improvement in multiple cognitive domains (attention and concentration, executive function, and memory), even in a non-Western population. Larger prospective studies are required to compare the degree of cognitive improvement following the common BS procedures, namely SG and RYGB.

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Conflicts of interest

There are no conflicts of interest.

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  [Table 1], [Table 2], [Table 3]


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