People with obesity who underwent bariatric surgery had stable cognition two years later, suggesting that bariatric surgery may mitigate the natural history of cognitive decline expected in people with obesity, according to investigators at Michigan Medicine.
"Since individuals with obesity experience more rapid cognitive decline than those without, stable cognition two years after bariatric surgery may be considered a success against historical trends, yet future controlled trials are needed to test this," said the study’s first author, Dr Evan Reynolds, lead statistician for the NeuroNetwork for Emerging Therapies at Michigan Medicine.
Using a collection of memory and language tests developed by the National Institutes of Health, as well as the Rey Auditory Verbal Learning Test, the research team assessed over 85 bariatric surgery patients at two-year follow up (77 (88.5%) participants that underwent sleeve gastrectomy and 10 (11.5%) that underwent gastric bypass surgery). They found that NIH Cognitive Battery test scores remained stable, with secondary executive function tests showing improvement. One of the memory assessments, however, declined following surgery.
The primary outcome, NIHTB-CB composite score, was stable following bariatric surgery (−0.4 (13.9), p=0.81,n=66). Among secondary outcomes, the NIHTB-CB dimensional card sorting test (executive function assessment), improved (+6.5 (19.9), p=0.01, n=66) while the Rey AVLT delayed recall test (memory assessment) declined (−0.24 (0.83), p=0.01, n=87) following surgery. Improvements to metabolic risk factors and diabetes complications were not associated with improvements to NIHTB-CB composite score. The other 4 NIHTB-CB subtests and Rey AVLT assessments of auditory learning and recognition were stable at follow-up.
While this current study is the largest to assess changes two years after bariatric surgery, researchers say, the results conflict with previous studies which found improved memory and executive functioning among similar patients.
"A previous study was primarily made up of patients who received gastric bypass, while our study was made up primarily of individuals that completed a sleeve gastrectomy," explained Reynolds. "To provide the best evidence on the effectiveness of bariatric surgery on cognition and potential differences between surgery types, we must conduct larger observational studies or randomised, controlled trials."
After bariatric surgery, improvements in diabetes complications, such as peripheral neuropathy, chronic kidney disease and retinopathy, were not associated with improved cognition.
"Metabolic factors, including diabetes and obesity, are associated with cognitive decline, but we still need to better understand how best to treat these factors to improve patients' cognitive outcomes," said senior author, Dr Brian Callaghan, a neurologist at University of Michigan Health and the Eva L Feldman, professor of neurology at U-M Medical School.
The findings were featured in the paper, ‘The Effect of Surgical Weight Loss on Cognition in Individuals with Class II/III Obesity’, published in The Journal of Nutrition, Health & Aging.