Background: Various epidemiological studies have found an association between noise exposure and sleep quality, but the mediating role of annoyance is unclear for this association.

Objectives: To investigate the effects of both objectively modeled road traffic noise exposure as well as noise annoyance on subjective and objective sleep quality measures.

Methods: 1375 randomly selected participants from Basel, Switzerland, were enrolled in a questionnaire survey in 2008 with follow-up one year later (1122 participants). We assessed sleep quality by using a standardized sleep disturbance score, as well as the level of annoyance with road traffic noise at home. Objective sleep efficiency data was collected in a nested diary study by means of actigraphy from 119 subjects for 1551 nights. Residential nocturnal exposure to road traffic noise was modeled using validated models. Data were analyzed with random intercept mixed-effects regression models.

Results: In the main study, self-reported sleep quality was strongly related to noise annoyance (p for trend<0.001) but only moderately correlated with modeled noise exposure (p=0.07). In the nested diary study objectively measured sleep efficiency was not related to annoyance (p=0.25) but correlated with modeled noise exposure (p=0.02). Strikingly, noise induced decreased sleep efficiency was even more significant for study participants who were not annoyed with traffic noise (p=0.001).

Conclusions: This study indicates that effects of nocturnal traffic noise on objective sleep quality are independent of perceived noise annoyance, whereas the association between self-reported sleep quality and noise is mediated by noise annoyance.