Bariatric Surgery Ups Epilepsy Risk

Bariatric surgery increased the risk of epilepsy, a retrospective Canadian study showed.

Over a minimum of 3 years follow-up, bariatric surgery patients had a 45% increased risk of developing epilepsy compared with people who did not have bariatric surgery (HR 1.45, 95% CI 1.35-1.56), reported Jorge Burneo, MD, MSPH, of Western University in London, Ontario, Canada, and colleagues.

Stroke during the follow-up period increased epilepsy risk for bariatric surgery patients (HR 14.03, 95% CI 4.26-46.25), they wrote in Neurology.

The findings echoed earlier research that showed elevated risks of epilepsy and seizures after gastric bypass surgery in Sweden. The Swedish study suggested “bariatric surgery may be an unrecognized epilepsy risk factor; however, this possible association has not been thoroughly explored,” Burneo and colleagues noted.

Late neurologic complications of bariatric procedures — defined as those that appear 3 to 20 months after surgery — occur in 5% to 16% of patients, they observed.

“Our findings suggest that epilepsy may be among these long-term neurological complications; however, the mechanism remains unclear,” they wrote.

Malabsorption may be a factor, the researchers suggested. “Although limited, some research investigating the role of micronutrient deficiencies in epilepsy exists,” they pointed out.

“One study observed significantly lower vitamin C, zinc, and copper levels among patients with epilepsy and no history of antiepileptic drug treatment relative to healthy controls,” they continued. “Another study of a small number of patients with epilepsy found that normalizing serum 25-hydroxy-vitamin D levels significantly reduced median seizure frequency by 40%.”

Burneo and colleagues used health administrative databases in Ontario, Canada to identify 16,958 adults who had bariatric surgery for obesity from July 2010 through December 2016 (exposed participants) and 622,514 adults who were hospitalized with a diagnosis of obesity but did not have bariatric surgery during the same period (unexposed participants).

The study excluded people with a history of seizures, epilepsy, seizure or epilepsy risk factors, psychiatric disorders, or substance abuse or dependence.

Mean age was about 47 and approximately two-thirds of participants were women. The study followed patients through December 2019.

Total and median follow-up was 3,691,411 and 5.8 person-years in the exposed cohort and 3,818,669 and 5.9 person-years in the unexposed cohort.

For the primary analysis, the researchers used inverse probability of treatment weighting to control for confounding. In the weighted cohorts, estimated rates of epilepsy were 50.1 per 100,000 person-years in the exposed group and 34.1 per 100,000 person-years in the unexposed group.

“We did not find that patients were at differential epilepsy risk as a function of the type of procedure received,” the researchers said. “However, we likely had insufficient power to detect differences in risk between the procedure types.”

Stroke was a significant risk factor for new-onset epilepsy in the exposed group. “However, the very wide confidence interval around this estimate (95% CI 4.26-46.25) indicates that we observed a small number of strokes,” Burneo and colleagues wrote. “Future research should seek to provide a more precise estimate of the effect of stroke occurring after bariatric surgery on epilepsy risk.”

A limitation of the analysis was that researchers could not assess obesity status or BMI throughout the study. Some obesity-related conditions may affect epilepsy risk, Burneo’s group noted.