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TL;DR
The experimental mouse model did not show a protective effect of topical caffeine on retinal damage, and the study's cross-sectional design limits causal inference.
Nutrients · 15 authors, 15 centres
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The experimental mouse model did not show a protective effect of topical caffeine on retinal damage, and the study's cross-sectional design limits causal inference.
Diabetic retinopathy (DR) is a major cause of vision loss in diabetes. The relationship between caffeine intake and DR risk is inconsistent in existing literature. Caffeine intake was assessed using a validated food frequency questionnaire. The experimental component used db/db mice (n=20) treated with topical caffeine eye drops (5 mg/mL) or vehicle for two weeks, assessing glial activation (GFAP expression) and vascular permeability (Evans Blue leakage). Key Results: In the clinical study, multivariable logistic regression showed that moderate (Q2) and high (Q4) caffeine intake quartiles were associated with a lower prevalence of DR compared to the lowest quartile (Q1), with odds ratios of 0.35 (95% CI 0.16-0.78; p=0.011) and 0.35 (95% CI 0.16-0.77; p=0.010), respectively. No significant association was found for coffee and tea consumption as continuous variables or quartiles. Hypertension, diabetes duration, and HbA1c were identified as risk factors for DR. Limitations: The cross-sectional design prevents establishing causality. The study is a sub-analysis of a previous study, and the sample size may limit statistical power. The experimental model did not replicate the clinical findings, suggesting other compounds in caffeinated beverages (e.g., antioxidants) might be involved. Implications: The findings suggest a potential protective association between moderate/high caffeine intake and DR in T2D, but the lack of effect in the animal model and the study's design indicate that further research is needed to clarify the mechanisms and confirm these results.