Association of silent ST-segment depression on one-hour ambulatory ECGs with exposure to industrial noise among blue-collar workers in Israel examined at different levels of ambient temperature--the CORDIS Study.

Background: Epidemiologic studies on the effects of ambient temperature or industrial noise on the cardiovascular system have usually focused on blood pressure. However, the ambulatory ECG may be a sensitive instrument for evaluating transient changes in the myocardium associated with exposure to such environmental stressors. In particular, the presence of silent ST-segment depression would strongly suggest transient myocardial ischemia.

Aim: To evaluate a possible association between exposure to ambient noise and temperature in the workplace and silent ST-segment depression on short-term ambulatory ECGs.

Methods: Between 1985 and 1987, approximately 6,000 factory workers in Israel were examined in the framework of the CORDIS study. Each worker underwent ambulatory ECG monitoring for one hour. Measurements were taken of the average exposure to noise and the ambient temperature. Complete data including analysis of the ST-segment on the ambulatory ECG were available for 3,747 blue-collar workers.

Results: After excluding subjects with a history of heart disease, among men, silent ST-segment depression was found to be most prevalent in those workers exposed to more than 80 dBA compared with those exposed to less than 70 dBA. (RR = 2,4, p = .1 for men and RR = 1.3, p = .37 for women. Silent ST-segment depression was more prevalent at ambient temperatures up to 20 degrees C than over 25 degrees C (RR = 1.4, p = .22 for men and RR = 2.0, p = .005 for women). These trends persisted after controlling for possible confounding variables, such as age, type of work, smoking, and relative weight; however, only the temperature effects in women remained statistically significant.

Conclusions: These findings suggest that silent ST-segment depression on ambulatory monitoring may be a sensitive measure of the cardiovascular response to exposure to physical stressors in the workplace. Exposures to noise and varying ambient temperature appear to have different effects on men and women.