Industrial Noise Exposure and Risk Factors for Cardiovascular Disease: Findings from the CORDIS Study.

Previous studies of the association between occupational noise exposure and cardiovascular disease (CVD) or risk factors for CVD are primarily either cross-sectional or retrospective, whereas the design of the CORDIS study was both cross-sectional and longitudinal. It had three phases: Phase I was conducted during 1985-87 among 6,016 employees from 21 factories. Recorded were medical, ergonomic, environmental (including noise levels at the various work stations) and psychological data. Phase II was conducted during 1988-90, at 18 of the 21 original factories and included similar data collected from 3,509 subjects. Phase III was conducted during the years 1995-96 and 4,995 workers who participated in Phases I and II completed questionnaires pertaining to medical, occupational and life style variables. Mortality and cancer morbidity data were obtained over an 8 year follow-up period for all subjects. Results from Phase I, revealed no association between noise exposure and resting blood pressure. Positive association was found for serum lipids in women and in young men. Noise annoyance had an additive effect on this outcome. In addition, recurrent daily noise exposure was found to be associated with elevated acute resting heart rate. Results of Phase II showed that chronic exposure to high noise levels during the 2-4 years of the follow-up resulted in changes of 3.9 mmHg in SBP and 3.3 mmHg in DBP, among workers performing complex jobs. In workers performing simple jobs these changes were 0.3 and 0.4 mmHg. Thus the type of work performed appears to be a significant factor. Results of Phase III revealed that there was a trend for positive association between past noise exposure measured at Phase I and 8 years incidence of cardiovascular morbidity, mortality and total mortality. This trend was statistically significant for total mortality (hazard ratio = 1.97, 95% CI 1.28-4.54) even after controlling for possible confounders. In summary, tests for association between noise exposure and cardiovascular risk factors, or cardiovascular morbidity and mortality, and total mortality have yielded mixed results. Reasons for this are discussed, as well as suggestions for further research.