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A population-based study on nighttime road traffic noiseand insomnia.

STUDY OBJECTIVES
The aims of the present study were to investigate how nighttime road traffic noise relates to self-reported symptoms of insomnia and sleep medication use.


METHODS
We used questionnaire data from the population-based study Health and Environment in Oslo (HELMILO) (2009-10) (N=13,019). The insomnia symptoms difficulties falling asleep, awakenings during the night and waking up too early in the morning, as well as self-reported sleep medication use were included as outcomes. Modeled noise levels (Lnight) were assigned to each participant's home address. For selecting covariates to the statistical model, we used a directed acyclic graph (DAG). The associations between noise and sleep were analyzed using logistic regression models.


RESULTS
After adjustment for potential confounders, we found an odds ratio (OR) of 1.05 [95 % confidence interval (CI): 1.01, 1.09] for the association between traffic noise and difficulties falling asleep, in the total study population. For the association between traffic noise and awakenings during the night, the OR was 1.04 (95 % CI: 1.00, 1.08) and for waking up too early, the OR was 1.06 (95 % CI: 1.02, 1.11). The effect estimates are given per 5 dB increase in traffic noise level (Lnight). Self-reported sleep medication use was not statistically significantly associated with traffic noise exposure.


CONCLUSIONS
In an adult population from Oslo, traffic noise was associated with difficulties falling asleep and waking up too early. These findings indicate that sleep quantity may be compromised for individuals living in areas highly exposed to nighttime traffic noise.