[Multifrequency attenuation patterns in age-related hearing loss: a longitudinal analysis using spline mixed-effects models].

Objective: Based on longitudinal audiological data, this study explores the multifrequency dynamic decline patterns of age-related hearing loss (ARHL) to provide a theoretical foundation for early screening and intervention of ARHL. Methods: A total of 111 patients who visited the Otolaryngology Department of PLA General Hospital between January 2009 and May 2025 and underwent at least two pure-tone audiometry tests with an interval of no less than one year were included. The inclusion criteria were as follows: aged 50 years or older at the first test, no history of high noise exposure, otitis media, or sudden deafness, and symmetrical hearing in both ears. Their longitudinal audiological data were analyzed, and a spline mixed-effects model was constructed using R. Natural spline basis functions were employed to fit the nonlinear effects of hearing threshold shifts across frequencies with age, meanwhile, the growth rates of each frequency, age effect coefficients (β), and hearing threshold trends were calculated across frequencies, while calculating annual progression rates and age effect coefficients (β) for each frequency. Results: The average age at the first test was (72.9±9.9) years, with follow-ups ranging from 2 to 17 times and an average test interval of (7.2±4.3) years (maximum interval: 14.9 years). The model revealed: ① Hearing thresholds increased nonlinearly with age across all frequencies (P<0.001), with the high-frequency group (6 000, 8 000 Hz) showing significantly higher age effect coefficients than the low-frequency group (125, 250 Hz) (8 000 Hz basis function B2: β=72.21, t=7.46 vs. 500 Hz basis function B3: β=39.12, t=9.95). ② The coefficient of PTA (mean of 500, 1 000, 2 000, 4 000 Hz) basis function B2 (β=46.97) was lower than the full-frequency mean (β=51.24), and its dynamic changes were highly synchronized with 2 000 Hz. ③ The 8000 Hz frequency exhibited the highest hearing threshold increase rate (1.10 dB/year), peaking at 70-74 years (1.39 dB/year) and declining to 0.56 dB/year at 90-100 years. In contrast, the 125 Hz rate increased steadily from 0 dB/year at 50-54 years to 1.04 dB/year at 80-84 years. Conclusions: The spline mixed-effects model accurately delineates the multifrequency nonlinear decline characteristics of ARHL, revealing a three-stage pattern of hearing deterioration across frequencies: "early progression in the elderly, mid-term acceleration, and late-stage deceleration." The strong correlation between 2 000 Hz and PTA suggests its potential value as a screening indicator.