Academic journal article Environmental Health Perspectives

Impacts of Subchronic, High-Level Noise Exposure on Sleep and Metabolic Parameters: A Juvenile Rodent Model

Academic journal article Environmental Health Perspectives

Impacts of Subchronic, High-Level Noise Exposure on Sleep and Metabolic Parameters: A Juvenile Rodent Model

Article excerpt

Introduction

A third of the world's population suffers from poor-quality sleep and/or a lack of sleep (Ohayon 2011). The main cause of these sleep disturbances is noise exposure (Goines and Hagler 2007). According to the Organisation for Economic Co-operation and Development, in 2001, 13% of European people, corresponding to 100 million, were exposed to noise levels exceeding 65 A-weighted decibels [dB(A)] (OECD 2001). This is despite the fact that 55 dB(A) noise is known to increase the secretion of hormones regulated by the autonomic nervous system and promotes awakening (Fouladi et al. 2012; Zare et al. 2016). Indeed, noise exposure is associated with both auditory and nonauditory effects (including sleep disturbances).

Sleep can be disturbed either directly (when exposure to noise occurs during the sleep period) or indirectly (as an aftereffect, when exposure occurs before the sleep period). Epidemiologic studies of populations living close to airport or major roads have shown that noise exposure during the rest period decreased subjective sleep quality (Frei et al. 2014), increased difficulty in falling asleep (Basner 2008), increased awakenings from sleep, and altered sleep stages [especially a reduction in the proportion of rapid eye movement (REM) sleep] (Hobson 1989; Weyde et al. 2017). Interventional studies in humans have shown that noise during the active period decreased REM sleep duration (Blois et al. 1980), while transient noise up to 71 dB(A) during the rest period did not modify REM duration but increased transient activation phases (Bach et al. 1991). In rats, environmental acute exposure (for 1 d) and pseudochronic exposure (for 9 d) to 85 dB noise during the rest period was found to fragment sleep and reduce the amount of REM sleep, the amount of non-REM (NREM) sleep, and the total sleep time (TST) (Mavanji et al. 2013; Parrish and Teske 2017).

Besides these effects on sleep, epidemiologic studies of adults have linked noise to hyperglycemia (Eze et al. 2017), elevated blood triglyceride levels (Axelsson and Lindgren 1985), elevated waist circumference, and obesity (Pyko et al. 2015). Although it is difficult to established whether these metabolic effects are mediated by sleep disturbances, the latter are known to modify certain metabolic functions, which in turn may result in body weight loss (Moraes et al. 2014) or gain (Michel et al. 2003).

In the literature, most investigators have evaluated the physiologic effects of acute or pseudochronic exposure to noise over periods ranging from 1 h to 9 d, with intensities of 85 to 90 dB (Mavanji et al. 2013; McCarthy et al. 1992; Rabat et al. 2005; Rabat 2007; Van Campen et al. 2002; Zheng and Ariizumi 2007). Only one study (in mice) assessed long-term, subchronic noise exposure (90 dB for 5 h/day over 4 wk), i.e., under conditions that are more representative of the environment commonly encountered by the human population (Zheng and Ariizumi 2007). All the above-cited studies were performed with either environmental noise or artificial (white) noise. Artificial noise is not always appropriate for experiments in the rat because the latter's auditory system is shifted toward higher frequencies than that of humans (Heffner et al. 1994). Environmental noise induced similar sleep disturbances in humans and in rats (PasschierVermeer and Passchier 2000; Rabat et al. 2004). Furthermore, in a rodent model, it was shown that environmental noise had a more harmful impact on sleep than continuous white noise did and a similar effect compared with intermittent white noise (Rabat et al. 2004). In the present study, we chose to combine environmental and white noise with a mean intensity of 87.5 dB; this corresponds to high-level exposure but does not perturb the rat's auditory functions, even when administered for long periods (Cappaert et al. 2000).

Most of the literature data on the effects of noise on sleep or metabolic functions were generated in studies of adults; this is despite the fact that sleep processes are particularly relevant for body growth, homeostasis, and brain and organ maturation in developing organisms (Porkka-Heiskanen 2013; Stansfeld and Clark 2015). …

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