Noise as a contributory factor in the development of elevated arterial pressure. A study of the mechanisms by which noise may raise blood pressure in man.

Arterial pressure and other hemodynamic variables (stroke volume (SV), cardiac output and total peripheral resistance) were studied in 18 healthy males before and during exposure to recorded industrial noise. All measurements took place under strictly standardized conditions in a noise laboratory. the frequency distribution and level of noise used for stimulation were continuously monitored and kept constant within close limits throughout the experiments. SV was measured with impedance cardiography. Indirect blood pressure (BP) in the brachial artery was measured with an automatic device and the derived parameters, cardiac output and total peripheral resistance, were calculated from these measurements. Compared with resting conditions at 40 dBA, stimulation with industrial noise at 95 dBA caused significant increases in diastolic BP, mean arterial pressure and total peripheral resistance. Minor but statistically significant reductions of SV and cardiac output were seen. Heart rate and systolic BP did not change. These alterations of the hemodynamic variables persisted throughout 20 min of noise stimulation and were maintained for 5 min following cessation of noise stimulation. All variables had returned to their initial levels 10 min after discontinuation of noise stimulation. This study suggests that exposure to industrial noise at levels prevailing during several industrial processes may cause acute elevations of arterial BP and peripheral vascular resistance. In animal studies, repeated elevations of BP due to exposure to noise have been shown to cause a permanent elevation of BP. Therefore, we suggest that noise may be one of several external stimuli contributing to the development of arterial hypertension in man.