Weight-loss surgery not a risk factor for diabetic retinopathy

For people with type 2 diabetes (T2D) and diabetic retinopathy (DR), bariatric surgery does not appear to confer any risk of DR progression, according to a study.

Among the 238,967 study participants with T2D and DR, those who underwent bariatric surgery did not have greater odds of experiencing DR worsening either in the short term (odds ratio [OR], 0.41, 95 percent confidence interval [CI], 0.13–1.33; p=0.14) or long term (OR, 0.64, 95 percent CI, 0.33–1.24; p=0.18). [Acta Diabetol 2023;60:1531-1539]

The estimates “suggested lower or equal rates of DR worsening in individuals who underwent bariatric surgery compared to persons who did not,” the investigators said.

“We found no accounts of either transient or long-term ocular treatment needs postsurgery in our case population except for less than five cases of intravitreal injections (too few events to statistically analyse),” they added.

The analyses were based on data from The Danish Registry of Diabetic Retinopathy that involved 238,967 individuals with T2D (median age 49 years, 63 percent women) who attended diabetic eye screening. Of these, 3,230 were included, of which 553 underwent bariatric surgery and 2,677 did not. Those in the bariatric surgery group had more comorbidities, lower HbA1c, as well as more frequent use of glucose-lowering and antihypertensive medications than controls at index date.

DR worsening rates (incident DR and progressive DR pooled) were 2.9 percent in the surgery group vs 5.2 percent in the control group at 6 months and 8.4 percent vs 7.9 percent, respectively, at 36 months.

Glycaemic stability

The positive results presented here are in line with data from recent, smaller studies suggesting that bariatric surgery does not contribute to the risk of DR incidence in patients with T2D. [Obes Rev 2017;18:309-316; Surg Obes Relat Dis 2017;13:352-360]

“Our nationwide data showed good baseline glycaemic stability amongst our case population, as well as a presurgical decline in HbA1c followed by a further postsurgical decrease in HbA1c, which might explain the low rates of progression,” the investigators pointed out.

However, evidence on the role of presurgical HbA1c levels with regard to DR progression is mixed. One study, for example, showed that a higher baseline HbA1c with a significant postsurgical drop was associated with increased risk of DR progression. Meanwhile, another study showed no such association. [Diabet Med 2015;32:1212-1220; Retina 2015;35:935-943]

It is also noteworthy that the rates of DR worsening among the study participants who underwent bariatric surgery were lower than that seen amongst the general screening population of patients with T2D in the Danish screening program. This, according to the investigators, indicates that patients eligible for bariatric surgery may have been following the presurgical guidelines that promote good presurgical glycaemic stability, in addition to adopting weight-loss interventions and lifestyle changes, all of which aimed at ensuring optimal outcomes following surgery. [https://endocrinology.dk/nbv/andre-endokrinologiske-sygdomme/fedmekirurgi/]

“Finally, our case population had a shorter diabetes duration than our control population, which might also be in the favour [of individuals who underwent bariatric surgery], considering the known association between diabetes duration and DR development,” they added.

The present study was limited by the lack of body mass index measurements and data on lifestyle factors (eg, smoking status, alcohol consumption, and other dietary choices). The study also relied on a screening database, which meant that the investigators did not have access to data from individuals with diabetes who never attended the DR screening program. Moreover, the data available for screening-specific outcomes were limited to the dates of screening.