Comment on “Reduced Complications and Improved Survival With Postoperative GLP-1 Receptor Agonist Use Following Lumbar Arthrodesis”

I congratulate Proffitt and colleagues on their recently published TriNetX-based retrospective cohort study which examined post-lumbar arthrodesis outcomes, comparing patients who had or had not received a post-operative glucagon-like peptide-1 receptor agonist (GLP-1RA) prescription. ¹ While TriNetX allows for the analysis of large, aggregate data, its streamlined nature can result in methodological biases remaining undetected by authors.^2,3 I am concerned that three biases are present in Proffitt and colleagues’ analysis which could underestimate the rate of postoperative complications in their GLP-1RA cohort.

Firstly, the authors included any patients who underwent spine fusion between January 2010 and November 2025. However, the vast majority of GLP-1RA use has occurred since 2020. ⁴ Therefore, while patients in the control cohort would be more evenly spread across the study period, a greater proportion of the GLP-1RA cohort would have underwent lumbar arthrodesis in the 2020s. Over the past 20 years, lumbar arthrodesis has been increasingly conducted in lower-risk outpatient settings ⁵ and post-operative complication rates of lumbar fusions have decreased. ⁶ It is therefore possible that the reduction in post-operative complications/mortality seen in the GLP-1RA cohort could be a result of secular improvements in surgical technique, rather than anything attributable to the drug.

Secondly, the authors do not censor patients with inadequate follow-up in their analysis. Their cohorts include patients who underwent surgery as late as November 2025. Therefore, patients who underwent surgery in 2025 would not have a full year of follow-up data to assess. While time-to-event analyses in TriNetX censors patients with inadequate follow-up, the risk ratio calculation tool in the TriNetX platform does not censor patients. ⁷ While this inadequate follow-up would only underestimate post-operative complications/mortality in the portion of patients who underwent surgery in 2025, this bias would disproportionately impact the GLP-1RA cohort as they would have received their surgeries on average more recently. This exact issue has been documented in a separate TriNetX-based study on GLP-1RA use. ⁸

I would therefore recommend that the results of this study be interpreted with caution, and that future research examining GLP-1RA use in lumbar arthrodesis uses a shorter study period and censors patients lost to follow-up.