Effects of nocturnal railway noise on sleep fragmentation in young and middle-aged subjects as a function of type of train and sound level Mahnaz Saremi ⁎, Jérôme Grenèche, Anne Bonnefond, Odile Rohmer, Arnaud Eschenlauer, Patricia Tassi Laboratoire d'Imagerie et de Neurosciences Cognitives (LINC-CNRS), 21 rue Becquerel, 67087 Strasbourg, France abstract article info Article history: Received 1 April 2008 Received in revised form 20 June 2008 Accepted 11 August 2008 Available online 22 August 2008 Keywords: Railway noise Sound level Sleep fragmentation Micro-arousal Age Due to undisputable effects of noise on sleep structure, especially in terms of sleep fragmentation, the expected development of railway transportation in the next few years might represent a potential risk factor for people living alongside the rail tracks. The aim of this study was to compare the effects of different types of train (freight, automotive, passenger) on arousal from sleep and to determine any differential impact as a function of sound level and age. Twenty young (16 women, 4 men; 25.8 years±2.6) and 18 middle-aged (15 women, 3 men; 52.2 years ±2.5) healthy subjects participated in three whole-night polysomnographic recordings including one control night (35 dBA), and two noisy nights with equivalent noise levels of 40 or 50 dB(A), respectively. Arousal responsiveness increased with sound level. It was the highest in S2 and the lowest in REM sleep. Micro-arousals (3–10 s) occurred at a rate of 25–30%, irrespective of the type of train. Awakenings (N 10 s) were produced more frequently by freight train than by automotive and passenger trains. Normal age-related changes in sleep were observed, but they were not aggravated by railway noise, thus questioning whether older persons are less sensitive to noise during sleep. These evidences led to the conclusion that microscopic detection of sleep fragmentation may provide advantageous information on sleep disturbances caused by environmental noises. © 2008 Elsevier B.V. All rights reserved. 1. Introduction The expected development of railway transportation in the next few years might be a potential risk factor especially at night for people living alongside the rail tracks. Nocturnal exposure to noise can primarily induce sleep disturbances in terms of difficulty to fall asleep, awakenings and alterations of sleep pattern or depth (Griefahn and Spreng, 2004; Ising and Kruppa, 2004; Muzet, 2007). Most of the studies conducted on the harmful effects of transportation noise, focused on aircraft (Raschke, 2004; Scheuch, 2004; Franssen et al., 2004; Basner and Samel, 2005) or road traffic noises (Hofman et al., 1995; Stansfeld et al., 2000; Öhrström and Skånberg, 2004). Only a few studies have been devoted to railway noise, since it is considered as the least disturbing noise on a subjective point of view. Miedema and Vos (2007) reanalyzed data from 24 field studies including almost 23,000 participants exposed to night-time traffic noise. They showed that at the same average noise exposure level, aircraft and road traffic noises are associated with more self-reported sleep disturbances than railway noise. By contrast, concerning the physiological reactivity to traffic noises, some laboratory studies have drawn opposite conclu- sions. Increased heart rate and finger pulse vasoconstriction have been reported after nocturnal exposure to railway noise compared to other traffic noises (i.e. jet airplane, truck, motorcycle) (Di Nisi et al., 1990). More recently, Griefahn et al. (2006), have conducted an experiment to compare the effects of noise emitted from aircraft, rail and road traffic on sleep. They reported that under the same equivalent noise levels, the same maximum levels and the same patterns during the night, sleep architecture was more severely affected by railway noise than by the other traffic noises. So, whether nocturnal exposure to railway noise influences sleep quality remains uncertain. In fact, this discrepancy could be due to the type of trains used in the different studies. It is known as a general rule that noise disturbances vary according to the physical characteristics of the noise events. The autonomic reactivity was found to be modified by stimulus intensity, duration and rise time during waking (Turpin et al., 1999) and sleeping (Berg et al., 1975; Hofman et al., 1995; Carter et al., 2002). Sleep disturbances, particularly in terms of awakenings, depend on physical characteristics of the noisy environment (Stansfeld et al., 2000; Muzet, 2007). It is therefore conceivable to assume that noises emitted from various types of trains exhibiting different physical characteristics would not produce similar effects. To our knowledge, no study directly assessed this question. Moreover, it could also be that reactivity to noise would not be the same depending on age, since elderly people complain much more than younger adults about environmental noise. Miedema and Vos (2007) have recently shown that the association of noise-induced sleep disturbance with age exhibits an inverse U-shape, with the strongest effect found between 50 and 56 years of age. However, since spontaneous awakening in this population during sleep is also more frequent (Wolkove et al., 2007), it is difficult to International Journal of Psychophysiology 70 (2008) 184–191 ⁎ Corresponding author. Tel.: +333 88 10 6247; fax: +33 3 88 10 6245. E-mail address: mahnaz.saremi@linc.u-strasbg.fr (M. Saremi). 0167-8760/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.ijpsycho.2008.08.002 Contents lists available at ScienceDirect International Journal of Psychophysiology journal homepage: www.elsevier.com/locate/ijpsycho