[Paper Review] Impact of Weight Loss on Brain Age: Improved Brain Health Following Bariatric Surgery

Yashar Zeighami, Mahsa Dadar+10 more|arXiv (Cornell University)|Dec 12, 2021

Cardiovascular Disease and Adiposity4 citations

TL;DR

This study investigates whether bariatric surgery-induced weight loss reverses obesity-related brain aging. Using MRI-based brain age prediction from voxel-wise morphometry, it shows a significant 2.9- to 5.6-year reduction in brain age at 12 and 24 months post-surgery, indicating improved brain health linked to metabolic improvements in BMI, blood pressure, and insulin resistance.

ABSTRACT

Overweight and obese individuals tend to have increased brain age, reflecting poorer brain health likely due to grey and white matter atrophy related to obesity. However, it is unclear if older brain age associated with obesity can be reversed following weight loss and cardiometabolic health improvement. The aim of this study was to assess the impact of weight loss and cardiometabolic improvement following bariatric surgery on brain health, as measured by change in brain age estimated based on voxel-based morphometry (VBM). We used three datasets: 1) CamCAN to train the brain age prediction model, 2) Human Connectome Project to investigate whether individuals with obesity have greater brain age than individuals with normal weight, and 3) pre-surgery, as well as 4, 12, and 24 month post-surgery data from participants (n=87) who underwent a bariatric surgery to investigate whether weight loss and cardiometabolic improvement as a result of bariatric surgery lowers the brain age. Our results from the HCP dataset showed a higher brain age for individuals with obesity compared to individuals with normal weight (p<0.0001). We also found significant improvement in brain health, indicated by a decrease of 2.9 and 5.6 years in adjusted delta age at 12 and 24 months following bariatric surgery compared to baseline (p<0.0005). While the overall effect seemed to be driven by a global change across all brain regions and not from a specific region, our exploratory analysis showed lower delta age in certain brain regions at 24 months. This reduced age was also associated with post-surgery improvements in BMI, systolic/diastolic blood pressure, and HOMA-IR (p<0.05). In conclusion, these results suggest that obesity-related brain health abnormalities might be reversed by bariatric surgery-induced weight loss and widespread improvements in cardiometabolic alterations.

Motivation & Objective

• To determine whether obesity is associated with increased brain age, reflecting poorer brain health.
• To assess whether bariatric surgery-induced weight loss and cardiometabolic improvement can reverse brain aging.
• To examine regional brain changes in relation to brain age reduction post-bariatric surgery.
• To identify associations between metabolic improvements and reductions in brain age.

Proposed method

• Trained a brain age prediction model using data from the Cambridge Center for Ageing and Neuroscience (CamCAN) dataset.
• Validated brain age differences between normal-weight and obese individuals using Human Connectome Project (HCP) data.
• Collected pre-surgical and post-surgical (4, 12, 24 months) MRI scans from 87 bariatric surgery patients.
• Applied voxel-based morphometry (VBM) to estimate brain age from structural MRI scans.
• Calculated delta age (predicted brain age minus chronological age) to assess brain health changes over time.
• Correlated changes in delta age with post-surgical improvements in BMI, blood pressure, and HOMA-IR.

Experimental results

Research questions

• RQ1 Is brain age higher in individuals with obesity compared to those with normal weight?
• RQ2 Does bariatric surgery lead to a reduction in brain age, indicating improved brain health?
• RQ3 Are regional brain changes associated with brain age reduction after bariatric surgery?
• RQ4 To what extent are improvements in BMI, blood pressure, and insulin resistance linked to reductions in brain age?

Key findings

• Individuals with obesity had a significantly higher brain age than normal-weight individuals (p < 0.0001) based on HCP data.
• At 12 months post-bariatric surgery, brain age decreased by 2.9 years on average compared to baseline (p < 0.0005).
• At 24 months post-surgery, brain age decreased by 5.6 years compared to baseline (p < 0.0005).
• The reduction in brain age was associated with improvements in BMI, systolic and diastolic blood pressure, and HOMA-IR (p < 0.05).
• Exploratory analysis revealed lower delta age in specific brain regions at 24 months post-surgery, though the overall effect was global.
• The observed brain age reduction suggests that obesity-related brain health decline may be reversible through weight loss and metabolic improvement.