Daytime noise load—a 24-hour problem?

This study examines the influence of daytime noise load on spontaneous EEG activity and on the plasma levels of pituitary hormones, cortisol, and catecholamines during wakefulness and subsequent night sleep. Twelve subjects participated in two experimental series lasting 60 h, during one of which they were exposed to 85 dB (A) industrial noise from 9:00 to 21:00 h. With closed eyes, the direct effects of noise exposure on the EEG were a slight blockade of the alpha and theta activity, and with open eyes increased theta, alpha, and beta power were found towards the evening ( p < 0.01). From the endocrine parameters, the oxytocin levels were elevated during noise load ( p < 0.01), the adrenaline levels were increased during the first 6 h of exposure ( p < 0.001), the noradrenaline levels were lowered during the whole time of exposure ( p < 0.001) and also the ACTH secretion responded, but less clearly. The other hormone levels were not changed or only in individual cases. After-effects on subsequent undisturbed night sleep were a reduction of REM sleep in the EEG activity ( p < 0.001), shortened sleep cycles ( p < 0.01) and an increase in slow-wave sleep during the second sleep cycle ( p < 0.01); in the hormonal data a tendency to higher prolactin levels and lower free adrenaline levels was found.