LETTER TO EDITOR
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|Year : 2010 | Volume
| Issue : 49 | Page : 283--284
Comment on "The state of the art of predicting noise-induced sleep disturbance in field settings"
Mathias Basner1, Barbara Griefahn2, Keneth I Hume3,
1 Unit for Experimental Psychiatry, Division of Sleep and Chronobiology, Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
2 Leibniz Research Centre for Working Environment and Human Factors at TU Dortmund University, Ardeystr. 67, 44139 Dortmund, Germany
3 Division of Health Science, BCHS, Manchester Metropolitan University, United Kingdom
Unit for Experimental Psychiatry, Division of Sleep and Chronobiology, Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, PA
|How to cite this article:|
Basner M, Griefahn B, Hume KI. Comment on "The state of the art of predicting noise-induced sleep disturbance in field settings".Noise Health 2010;12:283-284
|How to cite this URL:|
Basner M, Griefahn B, Hume KI. Comment on "The state of the art of predicting noise-induced sleep disturbance in field settings". Noise Health [serial online] 2010 [cited 2020 Sep 19 ];12:283-284
Available from: http://www.noiseandhealth.org/text.asp?2010/12/49/283/70508
In their manuscript "The state of the art of predicting noise-induced sleep disturbance in field settings," Fidell et al. critically discuss the validity of noise-induced sleep disturbance predictions. They question the utility of these predictions and claim that they do not offer "substantial useful guidance for policy or regulatory purposes". Although we appreciate the critical review and agree with many of the arguments brought forward by the authors, some of the statements require further discussion.
Fidell et al. state that "it is far from certain that physiological responses to noise during sleep have meaningful health consequences". This, of course, very much depends on the definition of health consequences. If only increases in the risk of cardiovascular disease are regarded as health consequences, then Fidell et al. are certainly right that there is no study directly showing this link. However, there are epidemiologic studies showing a causal link between sleep disorders like obstructive sleep apnea and cardiovascular endpoints,  and sleep fragmentation is one of the reasons believed to contribute to this risk. Health consequences can, and we believe they probably should, be defined in broader terms. For example, it has been shown that nocturnal aircraft noise exposure increases objectively assessed daytime sleepiness,  which is associated with higher rates of errors and accidents that are potentially fatal. 
Fidell et al. state that another "difficulty in attributing adverse health consequences to noise-related sleep disturbances is that humans are among the most adaptable species". While this is true, this adaptation was shown to be incomplete, even after many years of noise exposure and, especially, for cardiovascular parameters. ,, At the same time, we know very little about interindividual differences in the ability to adapt to noise and should, therefore, not conclude that everyone will adapt to the same degree.
We agree that different methodological approaches complicate comparing or pooling data from different studies. A generally accepted consensus on measurement technique and outcome variable would help to alleviate this problem for future studies. Although we do not want to promote one of the outcome measures, decision making should certainly not solely be based on behavioral awakenings, as this outcome measure is too insensitive and relevant noise effects on sleep will be missed. We strongly believe that there is enough evidence demonstrating that noise-induced changes in sleep macro- and microstructure relevantly impair restoration even if they are not accompanied by conscious awakenings. ,
Fidell et al. question the utility of dose-response relationships between single-event aircraft noise metrics and measures of sleep disturbance as slopes are "often unhelpfully shallow," "unambiguous inflection points cannot be identified" and the "acoustic measures account for only a small fraction of the variance". First, because of interindividual differences, it will be much harder to predict the response of an individual relative to the average response of a group of subjects, and it is the latter that is usually the basis for decision making. Second, it is no wonder that little variance is explained if an outcome measure as insensitive as behavioral awakenings is used in conjunction with screening windows that are too long and therefore decrease the signal to noise ratio. Hence, a second-order polynomial fit to the aggregated data of the DLR laboratory study explains a stunning 99.6% of the variance in EEG awakening probability.  For the less-controlled DLR field study,  this value drops to 40.8%, but is still substantial. As far as the shallow slopes are concerned, we have to remind ourselves that the dose-response functions refer to single aircraft noise events. Reaction probabilities of 10% for single events may well induce relevant degrees of sleep disturbance if experienced 100-times or more per night. Although we would very much favor unambiguous inflection points ourselves, they are the exception in nature that seems to favor continuous sigmoidal functions.
Sleep is indeed "a complex process whose quality can be influenced by many environmental and other factors". This complicates the attribution of sleep disturbance to noise, but it has nothing to do with the relevance of noise-induced sleep disturbance, much like the fact that there are other reasons for lung cancer does not mean smoking does not substantially increase its risk.
We also agree that results from a field study conducted at one airport cannot be simply transferred to another airport in a 1:1 fashion, unless airport operations and the populations living at both airports are very similar. However, if there are differences (e.g., in traffic patterns), and the differences relate to variables that have been shown to relevantly influence sleep and that are known for both airport scenarios, then it should be possible to adjust for the differences and improve the extrapolation of the results from airport 1 to airport 2. 
We further agree that limit values are not set by scientists but by politicians and legislators. However, we still think that science should guide this process and at least define a decision set for the political decision process. The recently published WHO Night Noise Guidelines for Europe  are a good example in this respect. Here, experts in the field defined consensus L night ranges that are linked to specific outcomes related to sleep disturbance and health. These will be very helpful and may facilitate consensus among politicians and legislators for the definition of future limit values.
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