Supplementary file 1_Air pollution exposure and cataract outcomes: a systematic review and pollutant-specific meta-analysis.docx

The pooled HR was 1.036 (95% CI, 0.988–1.086) per 1 µg/m³ increase in PM₂.₅, 1.041 (95% CI, 1.013–1.070) per 10 µg/m³ increase in NO₂, and 1.010 (95% CI, 0.983–1.038) per study-specific interquartile-range increase in black carbon. Heterogeneity was substantial for PM₂.₅ (I² = 99.68%) and NO₂ (I² = 86.04%) but lower for black carbon (I² = 33.41%). The highest-versus-lowest quartile analysis also showed a positive association for NO₂ (HR, 1.094; 95% CI, 1.057–1.133; I² = 0.11%), whereas corresponding PM₂.₅ and PM₁₀ estimates were not statistically significant.

Knapp–Hartung adjustment widened the NO₂ confidence intervals, indicating sensitivity to the small number of contributing studies.</p>Conclusion<p>NO₂ showed the most consistent association with cataract outcomes, whereas evidence for PM₂.₅ remained heterogeneous and that for black carbon was limited. Although these findings support further investigation of traffic-related and other ambient pollution mixtures in cataract epidemiology, the sensitivity of NO₂ estimates to small-study inference precludes firm causal conclusions.

Independent prospective studies with improved exposure assessment and standardized cataract phenotyping are needed.</p>Systematic Review Registration<p>crd.york.ac.uk/PROSPERO/recorddashboard#, identifier CRD420261509514.</p>