[Electrocardiogram change of workers after disengaging occupational noise exposure]

To examine electrocardiogram (ECG) change of workers after leaving occupational noise exposure.

In the first phase of the Guangzhou Biobank Cohort Study, 10413 Guangzhou residents aged 50 years or more received a face-to face interview including noise exposure history, a full medical check-up and laboratory tests in 2003 - 4. ECG examination was carried out using 12-lead MAC-CS ECG machine made in HP Ltd, Shanghai, China. ECG of every subject was independently diagnosed by two doctors who had obtained ECG diagnosis qualification.

(1) Among 10413 subjects, 70% were female, and more than half were aged 60-69 years. The mean age and education level in males were higher than those in females. (2) 2119 subjects (21.0%) were previously exposed to noise and were retired now. (3) The prevalence of ECG abnormality was respectively 82.4% and 79.1% in females and males. Rate of ECG abnormality increased with age in both females and males (P = 0.000), and was lower in females with higher education level (P = 0.000). There was not significant difference in ECG abnormality between workers previously exposed or unexposed to noise in both females and males (P > 0.05). 4 Comparing workers previously exposed to those unexposed to noise in both females and males, after adjusting for age, educational level and smoking status, the rates of arrhythmia, axes deviation, atria and ventricle hypertrophy, ST-T change and coronary artery syndrome were not significantly different (P > 0.05).

Our study showed that the prevalence of ECG abnormality was not significantly increased in workers previously exposed to noise and had left exposure now compared to those never exposed to noise. Because our study was cross section and occupational history was obtained from a questionnaire but was not confirmed by the companies, further study is needed.