Event-related analysis of awakenings due to road traffic noise at night –a polysomnographic field study

Abstract

Objectives/Introduction: Nocturnal traffic noise causes sleep disturbances in residents. Thus, knowledge about noise effects is important to help protect residents’ sleep and maintain health, well-being, and performance. In recent years, DLR has established exposure-response curves regarding the effects of aircraft and railway noise on the awakening probability of residents. However, such a curve has not yet been established for road traffic noise. Methods: We conducted a field study in residential areas where road traffic was the dominant noise source and noises were attributable to separate events. Forty healthy participants (mean age = 29.1, SD = 11.7; 26 females) that were free of sleep disorders were polysomnographically examined for five consecutive nights. Acoustic measurements were undertaken at the sleepers’ ear. The synchronous collection of electrophysiological and acoustic data allowed for an event-related analysis of noise events and associated awakenings. Results: The present analysis included 152 nocturnal recordings with a total of 11265 road traffic noise events within the participants’ sleep period. Participants were exposed to a median of 107 road traffic noise events per night. A random effects logistic regression model, including acoustic, sleep-related and participant-related (e.g. age) variables, revealed a significant increase in the awakening probability with increasing maximum sound pressure level of a noise event (p < 0.001). When holding all confounding variables constant at their respective sample median, the awakening probability per single noise event ranged from 0.5 % at 24.2 dB(A) to 3.8 % at 70 dB(A) maximum sound pressure level. Assuming an exposure of 107 noise events per night with maximum sound pressure level of 39.4 dB(A) (median) the model estimates on average one noise-induced awakening per night. Conclusions: The present study is of high ecological validity and provides for the first time an exposure-response curve regarding the effect of separate road traffic noise events on the awakening probability. Our study focussed on residential areas with moderate traffic density at night. Further investigations of urban areas with dense traffic are still needed, which, however, will require a novel methodological approach as an event-related analysis is no longer feasible. The ultimate goal will be to establish physiologically based noise protection measures