The impact of nocturnal road traffic noise, bedroom window orientation, and work-related stress on subjective sleep quality: results of a cross-sectional study among working women

Objective: To examine the effect of work-related stress and road noise exposure on self-rated sleep and potential additive interaction effects.

Methods: Sleep and predictor variables were surveyed within two subsamples with 2191 and 1764 working women in a cross-sectional study. Sleep was assessed using a single question on general sleep quality and four questions on specific sleep problems and subsequently dichotomized (poor sleep vs. no poor sleep). Work-related stress was operationalized by job strain and effort-reward imbalance. Nocturnal exposure to road traffic noise was assessed as (a) the orientation of the bedroom window to a quiet façade vs. a low-, medium- or high-trafficked street and (b) energy-equivalent sound pressure levels for night-time modelled at the most exposed façade (L_night). We distinguished between low (< 45 dB(A)), medium (45-50 dB(A)) and high exposure (> 50 dB(A)).

Results: Poor sleep was associated with job strain and effort-reward imbalance. The prevalence of poor sleep did not increase with increasing L_night, but bedroom window orientation showed a non-significant trend. A quiet façade had a protective effect on sleep in each L_night category. We found a non-significant trend for an additive interaction between bedroom window orientation and job strain.

Conclusion: Noise levels modelled for the most exposed façade likely overestimate the actual exposure and thus may not be a precise predictor of poor sleep. Bedroom window orientation seems more relevant. Potential additive interaction effects between bedroom window orientation and job strain should be considered when interpreting epidemiological study results on noise-induced sleep disturbances.