Hearing Impairment and Hypertension Associated with Long Term Occupational Exposure to Noise

Background: Noise induced hearing loss, a permanent bilateral hearing impairment due to long term exposure to high levels of noise, represents one of the most common occupational hazards. This historical cohort study was undertaken to evaluate the auditory effects of noise and to further examine the hypothesis that a link between noise exposure and hypertension exists. Methods: The study population consisted of 140 healthy male employees from a local petrochemical industry with a history of past and present exposure to noise and 140 matched healthy unexposed individuals from the same industry (reference group). A questionnaire with 40 items concerning age, sex, weight, height, length of employment, workplace noise level, and history of hypertension was administered. Furthermore, the subjects were physically examined, their blood pressure was taken under normal resting position and all underwent audiometry testing. Similarly, sound pressure level and octave band analyzing in different stations of the workplace were carried out for every employee, and then Leq was calculated. Results: The prevalence of hearing impairment in this study was 38.5% among the exposed and 7.8% among the unexposed group and the difference was statistically significant. Similarly, the prevalence of hypertension in the exposed group was significantly higher than that in the unexposed group. Conclusions: These findings provide corroborative evidence to further substantiate the notion that exposure to noise is associated with hearing impairment. They also support the proposition that long term occupational exposure to noise appears to be a risk factor for arterial hypertension.