Bariatric surgery increases the risk of epilepsy

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

Over a follow-up of at least 3 years, patients who had bariatric surgery had a 45% increased risk of developing epilepsy compared to those who had not had 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.

Strokes during the follow-up period increased the risk of epilepsy for patients undergoing bariatric surgery (HR 14.03, 95% CI 4.26-46.25), they wrote neurology.

The results echo previous research showing an increased risk of epilepsy and seizures after gastric bypass surgery in Sweden. The Swedish study suggested that “bariatric surgery may be an unrecognized risk factor for epilepsy; however, this possible association has not been thoroughly investigated,” noted Burneo and colleagues.

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

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

Malabsorption could be a factor, the researchers suggested. “Although limited, there is some research investigating the role of micronutrient deficiencies in epilepsy,” they noted.

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

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

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

The median age was about 47 and about two-thirds of the participants were women. The study followed patients until December 2019.

The total and median follow-up times were 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, researchers used the inverse probability of treatment weights to control for confounding. In the weighted cohorts, the estimated epilepsy rates 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 different risk of epilepsy depending on the type of surgery they received,” the researchers said. “However, we probably didn’t have enough power to identify risk differences between the types of procedures.”

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 attempt to provide a more accurate estimate of the impact of stroke after bariatric surgery on epilepsy risk.”

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