Nutrients · 8 authors, 4 centres
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This cross-sectional study of 35,557 UK Biobank participants found that higher coffee and tea consumption was associated with thicker macular retinal nerve fiber layer (mRNFL), a marker of neurodegeneration, with the strongest effects for 2–3 cups of coffee and ≥4 cups of tea daily. However, instant coffee consumption was associated with thinner mRNFL, and the cross-sectional design limits causal inference.
Coffee and tea contain caffeine and antioxidants, which may have neuroprotective effects. The retina, as an extension of the central nervous system, can be assessed via optical coherence tomography (OCT) to measure retinal nerve fiber layer (RNFL) thickness, a potential marker for neurodegeneration. This study investigated associations between self-reported coffee and tea consumption and macular RNFL (mRNFL) thickness in a large population cohort. Methods: This cross-sectional analysis included 35,557 participants from the UK Biobank who had baseline OCT measurements and no pre-existing neurodegenerative or ocular diseases. Coffee and tea intake were self-reported and categorized into four groups (0, 0.5–1, 2–3, ≥4 cups/day). mRNFL thickness was measured using spectral-domain OCT. Multivariable linear regression models adjusted for demographic, socioeconomic, lifestyle, and health-related covariates. Restricted cubic spline models explored non-linear associations. Key Results: Coffee consumption was associated with increased mRNFL thickness in the fully adjusted model (β = 0.13, 95% CI = 0.01–0.25), with a significant effect for 2–3 cups/day (β = 0.16, 95% CI = 0.03–0.30) and an inverted U-shaped association (p for non-linear = 0.01). Tea consumption was linearly associated with increased mRNFL thickness (β = 0.13, 95% CI = 0.01–0.26), particularly for ≥4 cups/day (β = 0.15, 95% CI = 0.01–0.29). Instant coffee consumption was independently associated with thinner mRNFL (β = −0.19, 95% CI = −0.29 to −0.10). No significant interaction between coffee and tea was observed (p = 0.84). Limitations: The cross-sectional design prevents causal inference. Self-reported intake is subject to recall bias, and OCT measurements were taken at different centers, potentially introducing measurement error. The study population was predominantly Caucasian and from the UK, limiting generalizability. Implications: The findings suggest a potential neuroprotective association of coffee and tea with retinal nerve fiber layer thickness, but the negative association with instant coffee highlights the need to consider coffee type. Longitudinal studies are needed to confirm causality and explore implications for neurodegenerative diseases.
