Fig. 2

This t illustrates the results of restricted cubic spline regression analysis assessing the associations between fractal dimension metrics (FractalDimC, FractalDimCa, and FractalDimCv) and hearing loss at different frequencies: 1 kHz, 2 kHz, 4 kHz, 8 kHz, and across the hFI. Panels (A–C) show the associations at 1 kHz, where FractalDimCa and FractalDimCv demonstrate significant inverse relationships with hearing thresholds. Panels (D–F) present the results at 2 kHz, highlighting a pronounced negative association for FractalDimCv. Panels (G–I) depict the analysis at 4 kHz, with notable inverse trends for FractalDimCa. Panels (J–L) cover 8 kHz, showing a consistent, though less pronounced, relationship for FractalDimCa and FractalDimC. Finally, Panels (M–O) summarize the hFI analysis, with all FD metrics indicating clear inverse associations. The solid lines represent central risk estimates, and the shaded areas denote 95% confidence intervals, adjusted for age, gender, smoking status, alcohol consumption, HP, CHD, DM, and HYP.