Extra - auditory Effects of Noise in Laboratory Animals : Focusing on the Relationship Between Noise and Sleep

Noise has both auditory and extra-auditory effects. Some of the most deleterious extra-auditory effects of noise are those leading to sleep disturbances. These disturbances seem to be related to both endogenous (physical parameters) and exogenous (sex, age) factors of noise. Despite correlative relations between noise level and awakenings, the scientific community has not reached consensus regarding a specific action of these factors on the different sleep stages. In animal research, 2 complementary main fields of research exist. One is focused on the positive modulation of sleep by tone stimulation. The other concerns noise-related sleep disturbances. The few studies that have investigated noise-related sleep disturbances suggest the following conclusions. First, sleep disturbances are greater upon exposure to environmental noise, whose frequency spectrum is characterized by high and ultrasonic sounds, than white noise. Second, unpredictability and pattern of noise events are responsible for extractions from both SWS and PS. Third, chronic exposure to noise permanently reduces and fragments sleep. Finally in chronic noise exposure, an inter-individual variability in SWS deficits develop and are correlated to a psychobiological profile related to an incapability to face 2 arousing ascending systems. Chronic noise-related sleep disturbances may arise due to imbalance and malfunctioning of the hypothalamo-pituitary-adrenal axis and may contribute to the development of pathology. Despite great efforts to reduce noise, it remains one of the main environmental problems of modern society. 48,71 This problem emerged during the end of the 20 th century in parallel with the huge development of human activities (airway, railway, and road traffic). According to the World Health Organization, in contrast to many other environmental problems, noise pollution continues to grow, accompanied by an increasing number of complaints from affected individuals. 13 Noise is not simply a local problem—it remains a global dilemma that disturbs everyone and calls for precautionary actions in any environmental planning situation. 13 After briefly summarizing the effects of noise in humans (especially effects on sleep), I will discuss 1) effects of noise on sleep in animals and 2) the neurobiologic mechanisms that explain how noise disturbs sleep. Effects of noise in humans In humans, noise is now recognized to cause important health problems. 73,92 Noise effects are divided into auditory and extra-auditory changes. 93 Although the auditory effects of noise have long been studied, 15,42 they are not responsible for most of the effects of noise on organisms. Noise-associated problems mainly are associated with extra-auditory perturbations, …