Gastric Bypass Surgery Associated With Lower Risk of Diabetic Retinopathy Development

Swedish patients with type 2 diabetes (T2D) and obesity who underwent gastric bypass surgery (GBP) exhibited a reduced risk of developing new diabetic retinopathy (DR), compared with those who did not undergo surgery. Results of the observational study, published in JAMA Ophthalmology, also showed no evidence of an increased occurrence of sight-threatening or treatment-requiring DR in patients with no DR at baseline.

Although bariatric surgery has been shown to improve metabolic control and remission of T2D, several long-term and short-term adverse effects have been reported. In addition, in most studies of GBP among patients with T2D and obesity, no aggravation of preexisting DR has been observed.

“However, there are reports describing sight-threatening postoperative deterioration in DR, suggesting that closer monitoring of these patients is desirable. Regression of DR has been described after bariatric surgery but not confirmed,” authors wrote.

In order to better understand the relationship between diabetic ocular complications in this patient population and completion of GBP, researchers analyzed data from 2 nationwide registers in Sweden. Deidentified register data from the Scandinavian Obesity Surgery registry (SOReg) and the National Diabetes Register (NDR) contain clinical information on patients undergoing bariatric surgery and from almost all those with T2D living in Sweden.

Investigators matched patients recorded in the SOReg who underwent GBP between 2007 and 2013 1:1 with patients from the NDR with diabetes who did not undergo surgery. Patients were matched based on sex, age, body mass index (BMI) and calendar time, while follow-up data were obtained until December 31, 2015.

A total of 5321 patients who had undergone surgery were matched with 5321 controls. Mean (SD) patient follow-up time was 4.5 (1.6) years and groups were similar in terms of sex, duration of diabetes, glycated hemoglobin (A1c) concentration, blood pressure, blood lipid levels, and renal function. However, patients who had undergone GBP were somewhat older (mean age 49 [9.5] years vs mean age 47.1 [11.5] years) than those who did not and had a slightly higher BMI. Researchers also found differences with regard to income, educational status, and marital status between the groups, with standardized differences of >10% for all factors.

Analyses revealed:

• Mean BMI and A1c concentration at baseline were 42.0 (5.7) and 7.6% (1.5%), respectively, in the GBP group and 40.9 (7.3) and 7.5% (1.5%), respectively, in the control group
• Mean duration of diabetes was 6.8 (6.3) years in the GBP group and 6.4 (6.4) years in the control group
• 188 patients in the GBP group and 317 patients in the control group developed new DR
• Risk for new DR was reduced in the patients who underwent GBP (hazard ratio [HR], 0.62 [95% CI, 0.49-0.78]; P < .001)
• Dominant risk factors for development of DR at baseline were diabetes duration, A1c concentration, use of insulin, glomerular filtration rate, and BMI
• Cumulative incidence of the development of sight-threatening diabetic macular edema was not different between the GBP group and controls (0.8% [95% CI, 0.6%-1.1%] vs 0.6% [95% CI, 0.4%-0.9%])

Researchers also found “no evidence of increased risk of the development of other sight-threatening or treatment-requiring diabetic ocular complications, such as proliferative DR and the need for intravitreal drug administration (GBP group, 0.9% [95% CI, 0.6%-1.2%]; controls, 0.6% [95% CI, 0.4%-0.9%]) or panretinal photocoagulation (GBP group, 1.6% [95% CI, 1.3%-2.1%]; controls, 2.3% [95% CI, 1.9%-2.8%]).”

Despite the encouraging findings, investigators warned rapid improvement in metabolic control as a result of bariatric surgery may entail a risk for deterioration in pre-existing DR. One trial assessing effects of semaglutide in patients with T2D found those taking the glucagon-like peptide-1 receptor agonist had a significantly increased risk for DR complications compared with placebo.

In the current study, researchers were unable to determine the development of diabetic macular edema outside the center of the macula, which is not associated with vision loss or requiring treatment, marking a limitation. Development of severe non-proliferative DR could also not be determined with certainty based on the data.

“These data support the view that, besides standard screening for DR, there is no need for extended ophthalmologic surveillance of patients with diabetes undergoing GBP surgery if there is no DR at baseline,” authors concluded.

Reference

Åkerblom H, Franzén S, Zhou C, et al. Association of gastric bypass surgery with risk of developing diabetic retinopathy among patients with obesity and type 2 diabetes in Sweden: an observational study. JAMA Ophthalmol. Published online January 14, 2021. doi:10.1001/jamaophthalmol.2020.5892