Traffic noise as a risk factor for myocardial infarction.

The hypothesis that road traffic noise causes ischaemic heart disease (IHD) was tested in several epidemiological studies in middle-aged men. The studies carried out in Caerphilly (Wales) and Bristol-Speedwell (England) suggested the daytime (6-22 h) outdoor traffic noise level category 65-70 dB(A) as a threshold for noise effects detectable. Based on risk factors, a relative risk greater than 1 was calculated for the incidence of major IHD (RR = 1.1) in both samples for the subjects in this highest noise category, those in the quietest (51-56 dB(A)) serving as a reference using multiple models. Also the prevalence of myocardial infarction (RR = 1.2 and 1.1), ECG ischaemia (RR = 1.2 and 1.4) and any IHD disease (RR = 1.2 and 1.2) showed relative risks slightly greater than 1 in this noise group. In contradiction, the observed incidence of major IHD showed relative risks below 1 in both samples in this traffic noise group. The case-control studies carried out in Berlin revealed relative risks above 1 on the incidence (RR = 1.3 and 1.2) and the prevalence (RR = 1.2) of myocardial infarction at outdoor traffic noise levels in the range of 71-80 dB(A) serving the men in the category below 61 dB(A) as a reference. None of the findings was statistically significant. The relevance of the results is discussed.