Nocturnal Traffic Noise and Morning Cognitive Performance

Abstract

Introduction: Exposure to traffic noise during nighttime is a growing problem. Annoyance and complaints about disturbed sleep are steadily increasing and hence call for noise protection. This study focused on the impact of nocturnal noise exposure to air, road, and rail traffic on sleep and performance. Methods: 72 subjects (40 ± 13 years, 32 male) were polysomnographically examined during 11 consecutive nights. A psychomotor vigilance task (PVT), a memory search task and an unstable tracking task were conducted after waking up in the morning. Traffic noise was played back in the laboratory during the night with 8 h time in bed. Each traffic mode consisted of five noise categories (maximum sound pressure level 45, 50, 55, 60 and 65 dBA) with 8 different noise events, i.e. 40 noise events in total. Therefore, between 40 and 120 noise events were realistically played back during single (AI, RO, RA, RORO), double (AIRO, AIRA, RORA) and triple (AIRORA) exposure nights. The design was complemented with a noise-free control night and carefully balanced. Mixed model ANOVA was used for statistical analyses. Results: Only mean reaction time in PVT increased significantly by 3.6 ms (± 1.3 ms SE, p = 0.0069) after exposure nights. Reaction time increased significantly both with an increasing number of noise events (between 4.5 and 4.9 ms) and with equivalent noise level LAS,eq (between 4.8 and 5.0 ms) compared to the control night. Different traffic modes, or single compared to combined exposure nights, did not lead to specific performance alterations. Furthermore, combined traffic noise exposure conditions did not lead to stronger performance impairments than the single exposure conditions; effects were less than additive. Conclusions: Sleep disruptions caused by different traffic modes seem to be uniform in the resulting performance decrements on the following day. Conflict of Interest: The authors declare that they have no conflict of interest.