Abstract
It is unclear which noise exposure time window and noise characteristics during nighttime are most detrimental for sleep quality in real-life settings. We conducted a field study with 105 volunteers wearing a wrist actimeter to record their sleep during seven days, together with concurrent outdoor noise measurements at their bedroom window. Actimetry-recorded sleep latency increased by 5.6 min (95% confidence interval (CI): 1.6 to 9.6 min) per 10 dB(A) increase in noise exposure during the first hour after bedtime. Actimetry-assessed sleep efficiency was significantly reduced by 2%–3% per 10 dB(A) increase in measured outdoor noise (Leq, 1h) for the last three hours of sleep. For self-reported sleepiness, noise exposure during the last hour prior to wake-up was most crucial, with an increase in the sleepiness score of 0.31 units (95% CI: 0.08 to 0.54) per 10 dB(A) Leq,1h. Associations for estimated indoor noise were not more pronounced than for outdoor noise. Taking noise events into consideration in addition to equivalent sound pressure levels (Leq) only marginally improved the statistical models. Our study provides evidence that matching the nighttime noise exposure time window to the individual’s diurnal sleep–wake pattern results in a better estimate of detrimental nighttime noise effects on sleep. We found that noise exposure at the beginning and the end of the sleep is most crucial for sleep quality.
Highlights
There is increasing epidemiological research demonstrating the negative effects of transportation noise exposure on various chronic diseases, such as cardiovascular disease [1,2,3,4], metabolic syndrome [5–9], depression [10,11,12], and cognitive functions [13,14,15,16]
Confronted with the challenge of how to sum up and weight noise events, we developed an acoustical metric, the intermittency ratio (IR), to characterize short-term temporal variations of transportation noise exposure [32]
In a large cohort study, we found some evidence that IR may have a modifying effect on the cardiovascular mortality risk [33]
Summary
There is increasing epidemiological research demonstrating the negative effects of transportation noise exposure on various chronic diseases, such as cardiovascular disease [1,2,3,4], metabolic syndrome [5–. It is possible to quantify reactions of sleepers to sound pressure level at the ear in field experiments using contrived exposure settings (i.e., reproducing noise in a controlled fashion with loudspeakers). This approach, does not adequately consider long-term habituation to a noise source, which may be relevant in a real-life situation at home. The study explored (i) the relevance of indoor noise compared to outdoor noise, (ii) the predictive contribution of IR to sleep effects in addition to equivalent continuous sound pressure levels (Leq,night ), and (iii) the effect of noise exposure at different times during the night. We tested potential effect modification by noise annoyance, noise sensitivity, and sex
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