Physiological reaction thresholds to vibration during sleep

Invited paper

Michael Smith

Occupational and env. medicine

Tuesday 2 june, 2015, 14:00 - 14:20

0.4 Brussels (189)

In the Night Noise Guidelines for Europe 2009, the World Health Organisation report that there is sufficient available evidence for biological effects of noise on sleep starting at L<sub>A,max,inside</sub>=32 dB. There are however no such thresholds for vibration. Vibration is expected to affect an increasing number of people living close to rail or trafficked roads. It was therefore the objective to determine at what vibration amplitudes the human body begins to respond during sleep. These reactions include cortical arousals and awakenings, alterations of sleep depth, and changes in cardiovascular activity. An experimental laboratory study was performed in a setting designed to closely resemble a home environment. Participants slept in the sleep laboratory for 5 consecutive nights, composed of a habituation night, a quiet control night, and three exposure nights. Sleep was measured using polysomnography, and heart rate measured using electrocardiogram (ECG). The study involved 18 young, healthy participants, free of self-reported sleep problems. Recruitment was balanced in such a way so as to have approximately equal numbers of men and women, and an even divide of noise-sensitive and non-noise-sensitive individuals. Noise and vibration levels were selected based on the findings of a pilot study. Exposure nights in the primary study subsequently composed of 36 simulated freight train passages, with low level noise (L<sub>AF,max</sub>=30dB) and vibration. Each series of 36 trains involved 12 trains per night with maximum vibration amplitudes of 0.2, 0.3 and 0.4 mm/s. Preliminary data suggest that alterations of sleep depth, cortical arousals, and changes in heart rate begin to occur between 0.2 and 0.3 mm/s. A more complete analysis and summary of the findings shall be presented at the conference.

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