Cognitive Function and Brain Plasticity in Obese Patients—The Impact of Bariatric Surgery

Background and Aim: Obesity adversely affects brain function, but the effect of bariatric surgery on cognitive function is still poorly evaluated. We assessed metabolic parameters and cognitive function in obese patients before and after bariatric surgery (RYGB). Methods: A 75g OGTT was performed in 10 nondiabetic obese patients (BMI 46.0±5.4 kg/m2; age 43.6±10.5 years; HbA1c 43.3±4.6 mmol/mol) before and 6-months after RYGB for measurements of metabolic parameters. Mini Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were administered; neuronal plasticity (NP) of the visual cortex was measured as change in ocular dominance after 120 min monocular deprivation. No subject with drugs or alcohol abuse, psychiatric illness, head injury, brain tumor, dementia, epilepsy, learning disorder, developmental disability, and impaired sensory function were included. Results: At baseline median MMSE score was 28.5 (range 25-30) and median MoCA score 26.5 (range 21-30), indicating early cognitive abnormalities (MoCA<26 points). Six months after RYGB, BMI decreased to 35.2±6.1 kg/m2 (p=0.004) and glucose tolerance did not change. HOMA-IR (from 5.1±2.3 to 1.6±1.1) and disposition index (from 3.3±4.6 to 35.0±41.0) all improved (p<0.05); post-OGTT GLP-1 increased from 5336.6±2262.6 to 11132.3±3412.2 pmol/lx120min (p<0.05) and fasting plasma leptin decreased from 80.0±46.7 to 13.1±6.6 pmol/l (p<0.008). NP increased from 0.03±0.1 to 0.11±0.14 (p<0.01). Cognitive performance improved in all subjects (MMSE: 30, range 28-30; MoCA: 28.5, range 24-30; both p=0.03 or less vs. baseline). There was no correlation between MoCA and metabolic changes though it was positively correlated with NP post-RYGB (p=0.04). Conclusion: Morbid obese subjects have subclinical cognitive impairments and brain plasticity alterations that significantly improve after RYGB. While no correlation was found between metabolic and hormonal changes, NP was positively associated with MoCA score.