Griefahn et al. Traffic Noise and Sleep
Autonomic Arousals Related to Traffic Noise during Sleep
Barbara Griefahn, MD, Univ-Prof1; Peter Bröde, Dipl-Math1; Anke Marks, PhD1; Mathias Basner, MD, MSc2
1Institute for Occupational Physiology at Dortmund University, Dortmund, Germany; 2Deutsches Zentrum für Luft- und Raumfahrt (DLR), Institute of Aerospace Medicine, Cologne, Germany
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 ex- posed 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 situa- tions without awakenings.
Keywords: Traffic noise, sleep, polysomnogram, event-related autonomic arousals, acoustic and situational influences
citation: Griefahn B; Bröde P; Marks A; Basner M. Autonomic arousals related to traffic noise during sleep. SLEEP 2008;31(4):569-577.
———————————————————————–
Conclusions
This report concerned HR alterations during sleep evoked by noises emitted from aircraft, rail-, and road vehicles with maxi- mum levels of 45-77 dBA. The response patterns were mainly determined by the occurrence or absence of awakenings.
In case of awakenings the cardiac responses consisted of monophasic HR elevations of more than one minute. This response was scarcely influenced by the acoustic parameters. The most significant influence arose from the momentary sleep stage at the time of stimulation. The HR elevation corresponded to the extent of the increase of the sympathetic tone that is largest and lowest when waking up from SWS and REM, respectively.
Without awakenings the HR response showed a biphasic pat- tern where an initial acceleration with a maximum after 4 to 11 s was followed by a deceleration to a minimum below the baseline after 12 to 23 s, followed by a consecutive increase towards baseline values. The extent and the pattern of this response were significantly determined by the traffic mode where railway noise caused the earliest and aircraft noise the latest in- crease. The strongest influence arose again from the sleep stage at the time of stimulation with largest alterations in REM sleep and lowest in SWS.
Neither of these responses decreased with the time of night indicating that habituation is not likely. A lack of habituation is the essential precondition for the interpretation of these responses as potentially pathogenetic. Whether there is a pathogenetic effect has to be proven in future studies. If so this is more likely for the strong heart rate response in case of simultaneous awakenings. This supports the view of those authors who regard awakenings as the strongest reaction to nocturnal noises and base their concepts for the protection of residents against the impact of nocturnal traffic noise on this criterion.