24 Jun Inter-individual difference in the Effects of noise on Sleep Fragmentation.
Summary: Environmental noise exposure disturbs sleep and impairs our recuperation and may contribute to long term negative health outcomes (and can make us rather cranky). In metro populations, common sources of this noise often come from aircraft, road vehicles and trains. Historically the policy relating to noise in the urban environment has been designed to protect the “average” sleeper. This study looks to investigate the degree of individual differences in noise related sleep fragmentation in an otherwise homogeneous population. Over 46.7% of the arousal from sleep probability was due to inter-individual differences in arousal from sleep. No clear identifier or bio-markers to identify persons likely to be susceptible to noise related arousals were mentioned in this article.
Methods: 69 healthy subjects (mean ± standard deviation 40 ± 13 years, range 18–68 years, 32 male). The trial was a randomized, balanced, double-blind, repeated measures laboratory study. The subjects were exposed to 11 nights of varying noise sources and volumes. Noise sources included train, road vehicles and aircraft (via recorded audio). Their sleep was recorded by standard polysomnography. Mixed-effects models of variance were used, controlling for reaction probability in noise-free control nights, age, sex, number of noise events, and study night.
Results: 40.5% of the total variance in awakening probability and 52.0% of the total variance in EEG arousal probability were explained by inter-individual differences. If the data set was restricted to nights (4 exposure nights with 80 noise events per night), 46.7% of the total variance in awakening probability and 57.9% of the total variance in EEG arousal probability were explained by inter-individual differences.
Conclusion/Discussion: The results seem to demonstrate that, even in a relatively homogeneous, healthy, adult study population, a considerable amount of the variance observed in noise-induced sleep disturbance can be explained by inter-individual differences. These differences in arousal cannot be explained by age, gender, or the specific study design aspects. It will be important to identify those at higher risk for noise induced sleep disturbance by identification of biomarkers of susceptibility for noise-induced sleep disturbance. These markers will help develop mitigation and therapeutic strategies. At the same time, noise policy needs to reflect the large individual differences in the susceptibility to noise-induced sleep disturbance. It may not be enough simply protecting an “average” sleeper.