Could bariatric surgery prevent severe COVID-19?

Individuals who have undergone bariatric surgery to treat obesity may have a reduced risk of developing severe COVID-19, according to a recent study.

“The research findings show that patients with obesity who achieved substantial and sustained weight loss with bariatric surgery prior to a COVID-19 infection reduced their risk of developing severe illness by 60 percent,” said study lead author Professor Ali Aminian, director of Cleveland Clinic’s Bariatric and Metabolic Institute, Cleveland, Ohio, US.

“Our study provides strong evidence that obesity is a modifiable risk factor for COVID-19 that can be improved through a successful weight-loss intervention,” he pointed out.

Using electronic health records from the Cleveland Clinic Health System up to March 1, 2021, researchers of this retrospective, observational study identified 20,212 adults aged 18–80 years (median age 46 years, 77.6 percent female) with obesity (BMI 35–80 kg/m²; median 45 kg/m²). Of these, 5,053 patients had undergone Roux-en-Y gastric bypass or sleeve gastrectomy between January 2004 and December 2017. They were propensity score-matched 1:3 with obese adults who had not undergone bariatric surgery (non-surgery group; n=15,159). The participants were followed up for a median 6.1 years.

Weight loss between enrolment and March 1, 2020 was greater among patients who underwent surgery than the non-surgery group (mean difference at 10 years, 18.6 percentage points; p<0.001), as was the reduction in BMI (mean difference 8.3 kg/m²; p<0.001). Patients who underwent surgery also had a reduced risk of all-cause (non-COVID-19) mortality* compared with the non-surgery group (4.7 percent vs 9.4 percent; adjusted hazard ratio [adjHR], 0.47, 95 percent confidence interval [CI], 0.38–0.57; p<0.001).

A total of 11,809 patients were assessed for COVID-19–related outcomes between March 1, 2020 and March 1, 2021 (n=2,958 and 8,851 in the surgery and non-surgery groups, respectively).

The proportion of patients with a positive SARS-CoV-2 test result did not significantly differ between the bariatric surgery and non-surgery groups (9.1 percent vs 8.7 percent; adjHR, 1.03, 95 percent CI, 0.87–1.22; p=0.71). [JAMA Surg 2021;doi:10.1001/jamasurg.2021.6496]

Patients in the surgery group had a significantly lower BMI than those in the non-surgery group at time of positive SARS-CoV-2 result (mean difference 7.9 kg/m²), as well as lower body weight (mean difference 20 kg) and HbA_1c levels (mean difference 1.2 percent; p<0.001 for all).

Patients diagnosed with COVID-19 who had undergone bariatric surgery almost halved their risk of hospitalization compared with the non-surgery group (15.5 percent vs 28.2 percent**; adjHR, 0.51, 95 percent CI, 0.35–0.76; p<0.001).

Patients who had undergone bariatric surgery were also significantly less likely to require supplemental oxygen (9.2 percent vs 22.3 percent**; adjHR, 0.37, 95 percent CI, 0.23–0.61; p<0.001) and had a lower risk of severe COVID-19 infection (a composite of intensive care unit admission, need for mechanical ventilation, or death; 3.9 percent vs 9.3 percent**; adjHR, 0.40, 95 percent CI, 0.18–0.86; p=0.02) than those in the non-surgery group.

There were two deaths in the surgery group compared with 21 in the non-surgery group.

“This study suggests that an emphasis on weight loss as a public health strategy can improve outcomes during the COVID-19 pandemic and future outbreaks or related infectious diseases,” said study senior author Dr Steven Nissen, Chief Academic Officer of the Heart, Vascular, and Thoracic Institute at Cleveland Clinic.

The mechanisms behind the benefits seen in the study are still uncertain, the authors said. “[P]atients with substantial and sustained weight loss were likely physically and physiologically better equipped to cope with an infection that has the potential for multiorgan involvement,” they said, noting the healthier status of patients in the surgery vs non-surgery group at time of COVID-19 diagnosis.

However, the authors pointed out that no firm conclusions can be drawn owing to the observational study design and relatively low incidence of COVID-19. As such, the results should be “hypothesis generating.” They also cautioned that the effects should not be interpreted as a benefit of a surgical vs non-surgical weight loss intervention. 

Severe COVID-19 risk reduction: Another benefit of bariatric surgery?

According to Professor Paulina Salminen from the Turku University Hospital, Turku, Finland, and co-authors in an editorial, the results also highlight the status of bariatric surgery, which is considered an elective procedure and was thus postponed during the COVID-19 pandemic. [JAMA Surg 2021;doi:10.1001/jamasurg.2021.6549]

“This approach, however, overlooks severe obesity as a life-threatening and life-limiting disease and does not acknowledge the intertwined double pandemic of COVID-19 and obesity,” they said.

“[M]etabolic surgery should be considered as medically necessary … COVID-19 should now be added to the long list of obesity comorbidities that can be mitigated by metabolic surgery,” they concluded.