October 6, 2010 (Vancouver, British Columbia) — Analysis of data from the National Health and Nutrition Examination Survey (NHANES) shows that chronic exposure to occupational noise may contribute to coronary heart disease, especially among young men who smoke .
Some small studies suggest that noise may increase the risk of coronary disease and hypertension, but the findings have not been consistent, so Dr Wenqi Gan (University of British Columbia, Vancouver) and colleagues examined a cross-section of NHANES participants, because the survey is representative of the whole US. The results of their study are published online October 5, 2010 in Occupational and Environmental Medicine.
The study includes 6307 participants from NHANES from 1999 to 2004, age 20 and older and employed at the time of the interview. Most of the 1236 participants who reported they are chronically exposed to loud noise at work (21.2%) are male (83.3%). The average age of the noise-exposed participants is 40, and they are more likely than the nonexposed participants to be white, have a lower level of education, smoke, and be exposed to secondhand smoke. They also have a higher average body-mass index and are more likely to be regular drinkers.
Compared with participants who are never exposed to loud noise at work, those chronically exposed to occupational noise have a two- to threefold increased prevalence of angina pectoris, MI, CHD, and isolated diastolic hypertension, the study shows. After adjustment for various covariates, the odds ratios for angina pectoris, coronary disease, and isolated diastolic hypertension are 2.91, 2.04, and 2.23, respectively.
The association of noise exposure with angina pectoris, MI, and coronary disease is particularly strong for participants who are over 50 years old, male, and current smokers. However, the study did not find a significant correlation between noise exposure and increased levels of cardiovascular biomarkers, including blood lipids and circulating inflammatory mediators.
"This study suggests that excess noise exposure in the workplace is an important occupational health issue and deserves special attention," the authors conclude. They suggest that noise may contribute to the risk of myocardial ischemia or infarction because it is a "potent external stressor," like sudden emotional stress or physical exertion, and thereby activates the sympathetic nervous system and endocrine system, leading to coronary vasoconstriction and subsequent partial or complete coronary occlusion in people with or without preexisting coronary atherosclerotic plaque. The stress of noise could also lead to disruption of a vulnerable coronary plaque, the authors suggest.
The researchers acknowledge that their study did not include participants who had been exposed to workplace noise in the past but no longer work in that environment, and "the temporal relationship between noise exposure and the development of coronary heart disease is uncertain. . . . Future prospective cohort studies are necessary to clarify the relationship between previous noise exposure and the risk of CHD."