For people with obesity, weight loss surgery may slow cognitive decline
A new study has found that people with obesity who underwent weight-loss – bariatric – surgery had stable cognition two years after, and their executive function improved. Although further research is needed, the researchers are counting their findings as a win, given the association between obesity and rapid cognitive decline.
Over the past 50 years, worldwide obesity rates have tripled, creating a widespread public health crisis. It’s projected that by 2030, nearly 50% of US adults will be affected by obesity. Along with managing the primary condition, obesity is associated with various comorbidities, including cognitive impairment.
A new study by researchers at the University of Michigan Institute for Healthcare Policy and Innovation has investigated the effect of bariatric surgery on obese individuals’ cognitive function.
Eighty-seven participants with a mean age of 46.8 completed the study; 73.6% were female, and 77.0% were white. Baseline measurements were taken, including fasting lipids, HbA1c (a measure of blood glucose control), blood pressure, height, weight, and body mass index (BMI). IQ, academic skills in reading and math, emotions and anxiety were measured. Cognition was assessed using the National Institutes of Health (NIH) Toolbox Cognition Battery (NIHTB-CB), which measures attention, executive function, episodic memory, working memory, and processing speed.
All participants had class II (BMI of 35 to less than 40) or class III (BMI of 40 or higher) obesity. At baseline, the mean BMI was 46.4 kg/m2, 27.6% had diabetes, and 28.7% were taking blood glucose-lowering medication. Some participants had diabetes complications such as neuropathy and retinopathy. Of the 87 participants, 77 (88.5%) underwent gastric sleeve surgery and 10 (11.5%) underwent gastric bypass. The primary outcome was the change in a participant’s NIHTB-CB score two years after surgery.
The mean NIHTB-CB score was above average and relatively unchanged at baseline (106.0) and two years after bariatric surgery (106.7). While one NIHTB-CB executive function subset significantly improved at follow-up, the other four subtests remained stable. In contrast, participants’ delayed recall memory significantly declined after surgery.
While all metabolic risk factors substantially improved following surgery, except for blood pressure and total cholesterol, no improvement to any metabolic risk factor was associated with improvement in cognition. No changes in diabetes complications were significantly associated with changes in NIHTB-CB score.
“Metabolic factors, including diabetes and obesity, are associated with cognitive decline, but we still need to better understand how to treat these factors to improve patients’ cognitive outcomes,” said Brian Callaghan, the study’s corresponding author.
While it’s the largest study to assess cognitive change two years after bariatric surgery, the findings conflict with those of the Longitudinal Assessment of Bariatric Surgery (LABS) study, which found that bariatric surgery generally, but not universally, improved both executive function and memory.
“That 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,” said Evan Reynolds, lead author of the current study.
The researchers say that the difference in surgeries may have contributed to differential cognitive changes between theirs and the LABS study or that the memory benefits from gastric sleeve surgery take longer to manifest. Large, observational studies are needed to provide the best evidence on the effectiveness of bariatric surgery on cognition, as well as the existence of confounding variables. Additionally, longer-term studies will determine if post-surgery cognitive changes reduce the risk of dementia.
“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,” Reynolds said.
The study was published in The Journal of Nutrition, Health & Aging.