Autonomic arousals related to traffic noise during sleep

Abstract

Aim: To analyze the heart rate (HR) response to traffic noise during sleep and the influence of acoustic parameters, time of night, and momentary sleep stage on these responses.

Participants: Twelve women and 12 men (19-28 years).

Measurements and results: The participants slept in the laboratory for 4 consecutive nights in each of 3 consecutive weeks and were exposed to aircraft, road, or rail traffic noise with weekly permutations. The 4 nights of each week consisted of a random sequence of a quiet night (32 dBA) and 3 nights during which aircraft, rail traffic, or road traffic noises occurred with maximum levels of 45-77 dBA. The polysomnogram and the electrocardiogram were recorded during all nights. In case of awakenings, the HR alterations consisted of monophasic elevations for >1 min, with mean maximum HR elevations of 30 bpm. Though obviously triggered by the noise events, the awakenings per se rather than the acoustical parameters determined the extent and pattern of the response. Without awakenings, HR responses were biphasic and consisted of initial accelerations with maximum HR elevations of about 9 bpm followed by decelerations below the baseline. These alterations were clearly influenced by the acoustic parameters (traffic mode, maximum level, rate of rise) as well as by the momentary sleep stage.

Conclusions: Cardiac responses did not habituate to traffic noise within the night and may therefore play a key role in promoting traffic noise induced cardiovascular disease. If so, these consequences are more likely for responses accompanied by awakenings than for situations without awakenings.

Figure 1

Mean increases and 95% confidence intervals (CI) of heart rates after transportation noises (aircraft, rail, and road traffic noise) that were associated with awakenings. Black line: abrupt awakenings that occurred in the same epoch as the stimulus. Grey line: delayed awakenings that occurred during the following epoch.

Figure 2

Mean increases and 95% confidence intervals of heart rates after transportation noises (aircraft, rail and road traffic noise) that were associated with awakenings that lasted 1 epoch (left panel), 2 epochs (middle panel), or more than 2 epochs (right panel).

Figure 3

Mean alterations and 95% confidence intervals of heart rates after transportation noises without awakenings. Aircraft noise (left panel), railway noise (middle panel), or road traffic noise (right panel).

Figure 4

Mean alterations of heart rates after transportation noises without awakenings. Black line flatter, grey line steeper rate of rise. Aircraft noise (left panel), railway noise (middle panel), or road traffic noise (right panel).