Purpose: The aim of the study was to investigate whether diabetes mellitus (DM) is an independent risk factor in sight-threatening thyroid eye disease (ST-TED) and explore the interaction of DM with other known risk factors in TED.
Methods: This was a retrospective cohort study and included 202 consecutive TED patients presenting between 2013 and 2019. Data collected included demography, history of smoking, thyroid dysmetabolism, and presence of DM, TED-duration, activity and severity, best-corrected visual acuity (BCVA), and follow-up. Primary outcome measure was development of ST-TED and secondary outcome measures included change in BCVA, activity, and bilateral ST-TED.
Results: Mean age of the cohort was 52.14 + 9.14 years and 74 (36%) were male. DM was present in 49 (24%) and a positive history of smoking in 65 (32%) TED patients. Cox's proportional hazards showed the presence of DM (hazard ratio [HR] 2.22; P = 0.02) and a positive history of smoking (HR 3.62; P = 0.003) were significant risk factors for development of ST-TED and dysthyroid optic neuropathy (DON). Older age was a risk factor (HR 1.05; P = 0.02) for DON. DM increased the risk of developing bilateral ST-TED (OR 4.14; P = 0.004). Median follow-up was 4 months (range 0.1-96 months). A linear mixed model to predict longitudinal interaction between risk factors, found TED patients in DM group were likely to have worsening of visual function and a positive history of smoking accentuated this adverse outcome.
Conclusion: DM and smoking are major independent risk factors predictive of ST-TED. Coexisting DM either singularly or in combination with smoking may predict worsening of visual function in TED patients.
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