The effect of the number of aircraft noise events on sleep quality

BackgroundBoth the WHO and the EC recommend the use of Lnight as the primary indicator for sleep disturbance. Still, a key question for noise policy is whether the prediction of sleep quality could be improved by taking the number of events into account in addition to Lnight.ObjectivesThe current paper investigates the association between sleep quality and the number of aircraft noise events. The first aim of this study was to investigate whether, for the purpose of predicting sleep quality measured by motility, the nummer of events is adequately represented in Lnight for the purpose of predicting sleep quality measured by motility. The second aim was to investigate whether the number of events at a given Lnight has an additional predictive value. In addition, it was explored whether the total number of events should be taken into account for the production of sleep quality, or only the number of events exceeding a certain sound pressure level.MethodsThis study is based on data of a field study among 418 people living within a range of 20 km from Amsterdam Airport Schiphol. The data from this study are well suited for this purpose, since for every subject both the number and the exposure level of events are available. Sleep quality was measured by motility, derived from actimeters worn on the wrist, and by self-reported sleep quality scored on a 11-point scale. Mixed linear regression models were built in a stepwise manner to predict sleep quality during a sleep period time.ResultsThe results show that, given a certain equivalent noise level, additional information on the overall number of events does not improve the prediction of sleep quality. However, the number of events above LAmax of 60 dB was related to an increase in mean motility, indicating lower sleep quality. No effect of number of events was found on self-reported sleep quality.ConclusionsThis study suggests that the number of events is more or less adequately represented in Lnight and only the number of high noise level events may have additional effects on sleep quality as measured by motility. This may be viewed as an indication that, in addition to Lnight, the number of events with a relatively high LAmax could be used as a basis for protection against noise-induced sleep disturbance.