Effects of Continuous and Intermittent Transportation Noise on Sleep Fragmentation

Nocturnal transportation noise disturbs sleep by causing awakenings, sleep-stage changes or EEG arousals. However, it is unclear which acoustical characteristics cause these effects. Nineteen healthy participants (age range 19-69 y) were exposed to four different nighttime noise scenarios along with two quiet nights. Scenarios varied with respect to short-term exposure variation over time [Intermittency Ratio (IR) low, medium or high] and source (road or train), but had a constant hourly Leq of 45 dB(A) at the sleeper's ear. Sleep and EEG arousals were scored according to standard criteria. There was no significant difference in any of the global sleep variables (e.g. TST) between nights. However, the percentage change for arousals in NREM sleep was significantly higher during nights with high intermittency as compared to low, medium intermittency and quiet nights, whereas percentage change for arousals in REM sleep was significantly higher for all noise scenarios as compared to the quiet nights. REM sleep seems particularly susceptible to fragmenting effects of nocturnal transportation noise independent of IR. On the other side, the IR plays a role in disturbing NREM sleep. This needs to be confirmed by arousal probability analyses.