Combined Effect of Noise and Smoking on the Cognitive Performance ‎ of Automotive Industry Workers

Introduction: Noise is an environmental stressor and can cause or exacerbate mental disorders along with other stressors, and even affect the individual performance in certain conditions. The aim of this study was to evaluate the combined effects of noise and smoking on cognitive performance of the workers in an automotive industry. Methods: This is a descriptive-analytical study with cross-sectional design conducted on 300 workers randomly assigned into two groups of noise-exposed and non-exposed. They were examined using computerized tests including the Tower of London (TOL) test, Continuous Performance Test (CPT), and Stroop test. The sound pressure levels were measured based on an 8-hour equal-loudness contour in each group according to ISO 9612 standard, using the Testo CEL-815 sound level meter. Results: Two-way ANOVA results on 12 CPT variables showed that both noise and smoking had significant effects on the number of errors and correct responses to the third 50 stimuli set (of 150 stimuli), and on the number of errors and correct responses to the second 50 stimuli set with P<0.001, P <0.001, P-values= 0.012 and P-values <0.001 for smokers respectively, but only noise affected the other 7 indicators (P-values <0.001). Conclusion: Smoking and noise had negative impacts on concentration, attention and cognitive processing speed which can lead to individual mistakes and delayed decision making at the workplace.