Review: extraaural health effects of chronic noise exposure in humans.

Thirty-one epidemiologic studies published in the English literature since 1980 were reviewed to integrate the findings on effects of chronic industrial and traffic noise exposure on circulatory and cardiovascular diseases. Methodologic issues relevant to quantifying noise-induced risk are discussed. Although there has been some improvement over the decade, the quality of the research remains low. Cross-sectional studies continue to dominate. Studies to date show contradictory results, neither confirming nor invalidating the hypothesis that persons with prolonged exposure to high noise levels have an increased risk of high blood pressure and cardiovascular disease. Prevalence ratios for hypertension between high and low noise groups range from 0 to 3.1. The more methodologically rigorous studies report the lower associations. Differences in mean blood pressures detected have been relatively small, ranging from 0-10 mm Hg. No consistent pattern of findings on cardiovascular effects other than blood pressure has been reported. It is concluded that the quality of the research remains inadequate or inadequately reported for quantifying noise-induced risk. Prospective studies whose design accounts for potential confounding variables and effect modifiers are required before useful inferences may be drawn.