A number of studies have demonstrated that solvents may induce auditory dysfunction. However, there is still little knowledge regarding the main signs and symptoms of solvent-induced hearing loss (SIHL). A study was done to investigate the association between solvent exposure and adverse effects on peripheral and central auditory functioning with a comprehensive audiological test battery.

Seventy-two solvent-exposed workers and 72 non-exposed workers were selected to participate in the study. The test battery comprised pure-tone audiometry (PTA), transient evoked otoacoustic emissions (TEOAE), Random Gap Detection (RGD) and Hearing-in-Noise test (HINT).

A convenient summary of the audiogram for each ear is the pure-tone average (PTA) of thresholds measured at specific frequencies.As the PTA increases, the hearing ability decrease. The following table reports bivariate and multivariate linear regression results for the PTA outcome.

Solvent exp: EXP: solvent-exposed group, NEXP: non-exposed group (reference)

Tenure: number of years working at the factory exposed to solvents

Cigarettes: Number of cigarettes smoked per week

Alcohol: Number of drinks per month

ShootWP: history of shooting practice wearing hearing protection; ShootNP: history of shooting practice without wearing hearing protection; No shoot: absence of shooting practice (reference)

Pastnoise: history of previous occupational noise exposure (PNE)

Interaction age*solvent: factor of age times solvent group (exposed versus non-exposed)

A.Why is there a significant association between age and PTA in the bivariate model, but not the multivariate model?

Bivariate model Multivariate model Characteristic Beta P Beta P Age 0.411 p