Objective: To investigate the relationship between occupational noise exposure and blood pressure.
Methods: We studied 8811 workers at a metallurgical factory, who were exposed to different levels of noise at the worksite: < or = 80 dB for 8078 workers and > 80 dB for 733 workers. A clinical examination, including measurements of blood pressure (by mercury sphygmomanometer, Korotkoff phases I and V), heart rate (by pulse palpation), body weight and height, was performed. The subjects were stratified into four age groups (18-30, 31-40, 41-50 and > 50 years) and into two body mass index groups: normal weight (< or = 25 kg/m2) and overweight (> 25 kg/m2). In order to eliminate possible confounding factors and statistical bias, a retrospective case versus control analysis was also carried out.
Results: The epidemiologic approach showed that the systolic blood pressure (SBP) but neither the diastolic blood pressure (DBP) nor the heart rate values were statistically higher in the group who were exposed to noise levels of > 80 dB, although the difference could be considered clinically relevant only in the older age group. The prevalence of hypertension (according to World Health Organization criteria) was higher among the workers who were exposed to the higher levels of noise. Stratification for body mass index confirmed the existence of a higher prevalence of hypertension in the exposed group. The results from the case versus control analysis indicated that both the SBP and the DBP levels in the exposed group were significantly higher than those in the reference group, and confirmed the existence of a higher prevalence of hypertension in the exposed group.
Conclusions: The present data suggest that occupational exposure to noise levels exceeding 80 dB may lead to a higher prevalence of hypertension and to increased blood pressure values, although the results appear quantitatively different according to the approach that is taken to the problem (i.e. the epidemiologic or the case versus control approach).