Thursday, January 19, 2006

Noise, Blood Pressure and Cardiovascular Disease

Noise, Blood Pressure and Cardiovascular Disease

Recently, a systematic review of the scientific literature was published in the journal maintained by the National Institute for Environmental Health Sciences[1]. The investigators conducted a meta-analysis of 43 epidemiologic studies published between 1970 and 1999 that investigate the relation between noise exposure (both occupational and community) and blood pressure and/or ischemic heart disease (International Classification of Diseases, Ninth Revision, codes 410-414). The investigators studied a wide range of effects, from blood pressure changes to a myocardial infarction. With respect to the association between noise exposure and blood pressure, small blood pressure differences were evident.The investigators concluded that their meta-analysis showed a significant association for both occupational noise exposure and air traffic noise exposure and hypertension: We estimated relative risks per 5 dB(A) noise increase of 1.14 (1.01-1.29) and 1.26 (1.14-1.39), respectively. The investigators concluded that noise exposure can contribute to the prevalence of cardiovascular disease, but that the evidence for a relation between noise exposure and ischemic heart disease is still inconclusive because of the limitations in exposure characterization, adjustment for important confounders, and the occurrence of publication bias. They noted that the literature suggests that noise induced cardiovascular effects must be seen as a consequence of stress.

BrooklynDodger Comments. “Meta-analysis” is a recent scientific procedure to draw conclusions from a diverse group of scientific studies. Certainly 43 studies of noise, hypertension and high blood pressure should be enough to settle the question about whether there is a relationship. These Dutch governmental investigators concluded that noise exposure causes high blood pressure. High blood pressure, unless treated, leads to heart disease and stroke.

Progress on noise control stalled in the 1980’s, when the OSHRC ruled that employers could rely on hearing protection devices in most situations. NIOSH since has concluded that HPD’s provide only about 10 dBA of noise reduction, and that a significant fraction of persons exposed at 80 dBA will suffer hearing loss.[2] Therefore, the practical limit of HPD’s is really 90 dBA. Nevertheless, many people take the attitude that occupational hearing loss is not enough of a material impairment to health that it’s worth preventing.

These new studies provide the start for a quantitative exposure response relationship between noise and severe or life threatening health conditions. They should energized the campaign for reducing noise exposure through engineering controls.

[A little snarky, but if this is a "systematic" review, what would an "unsystematic review be?]

[1] van Kempen EE, Kruize H, Boshuizen HC, Ameling CB, Staatsen BA, de Hollander AE. The association between noise exposure and blood pressure and ischemic heart disease: a meta-analysis.” Environ Health Perspect. 2002 Mar;110(3):307-17.

[2] NIOSH, CRITERIA FOR A RECOMMENDED STANDARD, Occupational Noise Exposure, Revised Criteria 1998 DHHS (NIOSH) Publication No. 98-126

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