Early changes in cognitive function following bariatric surgery: evidence for rapid improvement or practice effects?

Metabolic bariatric surgery (MBS) is associated with postoperative improvement in neuropsychological test performance and recent work raises the possibility that these gains may emerge within weeks of surgery. However, repeat testing across brief postoperative intervals introduces the possibility of measurement error that artificially increases test scores and distorts understanding of postoperative changes.

Examine cognitive function prior to and 1-month following bariatric surgery.

University Hospital.

A total of 111 MBS participants completed the NIH Toolbox for the Assessment of Neurological and Behavioral Function test battery before and 1-month after MBS as part of a larger project.

Repeated measures analysis of covariance revealed improved cognitive test scores following both Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG), though reliability change metrics could not rule out contribution from practice effects. Receiver operating characteristic analyses revealed that lower preoperative body mass index (BMI) was associated with greater likelihood of true cognitive improvement post-MBS on the Pattern Comparison subtest of the NIH Toolbox (area under the curve = .65, 95% confidence interval .53-.76).

Though both RYGB and SG patients exhibited improved cognitive function 1-month postoperatively, the current results suggest these early gains should be interpreted cautiously as they may reflect more than just neurobiological factors. Preoperative BMI may predict cognitive trajectory post-MBS, though future research is needed to refine cognitive testing procedures with the goals of clarifying the timeline of neurological changes postoperatively and whether MBS may reduce risk of Alzheimer disease and other risk factors for cognitive decline.