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BACKGROUND: Noise is an environmental factor that has been associated with metabolic and sleep disorders. Sleep is a vital function, since it underpins physiologic processes and cognitive recovery and development. However, the effects of chronic noise exposure on the developing organism are still subject to debate.

OBJECTIVE: The objective of the present study was to assess the effects of suhchronic, high-level noise exposure on sleep, apnea, and homeostasis in juvenile rats.

METHODS: Twenty-four 3-Wk-old male Wistar rats were exposed to noise [87.5 decibels (dB), 50-20,000 Hz for 5 wk and 2 d during the 12-h rest period. Data on sleep stages, food and water intake, apnea, and body and organ weight were recorded.

RESULTS: Five weeks of high-level noise exposure were associated with hypeiphagia (+15%), body weight gain (+6%), a heavier thymus (+26%), and heavier adrenal glands (+117%). A sleep analysis highlighted microstructural differences in the active period: in particular, the mean daily amount of rapid eye movement (REM) sleep as a proportion of total sleep time (TST) was higher. The mean daily amount of non-REM (NREM) sleep was lower in the exposed group, meaning that the intergroup difference in the TST was not significant. During a 1-h, noise-free plethysmographic recording during the rest period, the mean total amount of active wakefulness (AW) was lower in the exposed group (by 9.1 min), whereas the mean duration of an episode of REM sleep was higher (by 1.8 min), and the TST was higher (by 10.7 min).

DISCUSSION: Subchronic exposure of juvenile rats to high-intensity noise during the rest period was associated with some small but significant sleep disturbances, greater food and water intakes, greater body weight gain, and greater thymus and adrenal gland weights. The main effects of noise exposure on sleep were also observed in the 1-h plethysmography session after 5 wk of exposure.