by Daniel Fink, MD, Chair, The Quiet Coalition
Could noise be a risk factor for hypertension? This fascinating study from Chengdu, China, suggests that the answer is yes. The study design is innovative. The investigators measured bilateral high frequency hearing loss (BHFHL) and blood pressure in 21,000 workers, with an average age of 40. Hearing loss was a proxy measure for occupational noise exposure. Workers with greater hearing loss, as measured by audiometric tests, had a greater risk of also having high blood pressure.
The study is an exploratory one, and it is cross-sectional, i.e., the workers were not followed for decades and the study is based on one-time measurements of hearing and blood pressure. Other factors known to be associated with hypertension, such as weight and alcohol consumption, were not documented. And only a proxy measure of occupational noise exposure, bilateral high frequency hearing loss, was used, rather than actual noise measurements in the workplace. But the number of workers studied was large enough to provide high statistical significance, and the results were striking. As the researchers noted, “subjects having mild and high BHFHL had a higher hypertension risk of 34% and 281%, respectively (both P<0.001). Dose-response relationship between BHFHL and hypertension was found in both males and females.”
Studies done in the U.S. also show a correlation between occupational noise exposure and hypertension. The Chinese study may show a stronger relationship between occupational noise exposure and hypertension because workplace protections and their enforcement may be less stringent in China than in the U.S.
What are the implications of this study for public health? More than 100 million Americans have high blood pressure. At least two studies show that noise exposure in everyday life is great enough to cause hearing loss. Is it also great enough to contribute to the epidemic of hypertension in the U.S.?