The impact of arterial sclerosis on hearing with and without occupational noise exposure: a population-based aging study in males

Arterial sclerosis contributes to inadequate blood supply to multiple organs, suggesting that general atherosclerosis may play an important role in the inner ear. Since noise is a major etiology for hearing loss, the aim of this study was to evaluate both the respective and the combined effects of arterial sclerosis and occupational noise exposure on hearing after accounting for age in middle-aged and elderly men.

The evaluation was conducted using 773 subjects from a population-based sample of 1189 men, aged 40-83 years. The impact of carotid atherosclerosis (CA) or retinal arteriolosclerosis (RA) on hearing was assessed according to history of occupational noise exposure (Noise) obtained in a questionnaire. Differences in the mean pure-tone thresholds at each frequency, between the CA (+) and CA (-) groups or between the RA (+) and RA (-) groups, based on noise exposure were compared using the general linear model (GLM) Procedure in SAS, with adjustments for age. Then, the main effect of CA or RA, and the interactive effect of noise and either CA or RA on pure-tone threshold at seven frequencies were analyzed using an analysis of covariance (ANCOVA), after adjusting for age.

In the Noise (+) group, a statistically significant deterioration in hearing was found in the CA (+) group compared with the CA (-) group at 500 and 1000 Hz. The results in RA were significant at even lower frequencies than in CA. In the results from ANCOVA, the significant main effect of CA was shown in the pure-tone threshold at 8000 Hz, but not in the analysis of RA. A significant interactive effect of either CA or RA and Noise was observed in hearing at the range from 125 to 1000 Hz.

The present study suggests that the impact of arterial sclerosis on hearing is limited but significantly hazardous in middle-aged and elderly men, and that arterial sclerosis exacerbates the deleterious effects of noise on hearing. Early recognition of arterial sclerosis might be contributory to the hearing prognosis after middle age, especially for noise-exposed men.