Combined effect of smoking and occupational noise exposure on hearing

ABSTRACT

Although noise and smoking are frequently encountered hazards in the occupational settings, and they may act in common causal pathways for hearing loss, yet, the combined effects involving smoking and noise have rarely been assessed. To study the combined effect of smoking and noise on hearing loss. A cross sectional comparative study was adopted. The study included 196 male smokers, and 154 male non smokers from a wood processing factory, where workers were exposed to noise levels exceeding 85 dBA. All workers were subjected to a] an interviewing schedule to collect data about personal characteristics, smoking habit, duration of military service, current working conditions, and manifestations related to noise exposure, b] physical examination, and c] audiometric measurements for assessing hearing acuity. It was observed that noise exposed smokers had a significant high prevalence of hypertension, Raynaud's phenomenon and self reported hearing loss compared with non-smokers exposed to the same noise intensity. Moreover, noise exposed smokers had a significantly higher mean hearing loss [%] and a higher mean hearing threshold at the frequency 4000Hz compared with non smokers. When age groups and smoking index were studied in relation to hearing loss, noise exposed smokers above the age of 40 years had a significant increase in the mean hearing loss percent compared with non- smokers in the same age group, and heavy smokers had a significant increased prevalence of hearing loss compared with mild and moderate smokers. Furthermore, after allowing for the effects of age and duration of noise exposure, current smokers were 4.16 times at a higher risk of developing hearing loss compared with non smokers. Smoking aggravates noise induced hearing loss specialy after the age of forty, and accurate follow up of smokers who are exposed to hazardous noise is suggested