Habituation of sleep to road traffic noise as determined by polysomnography and an accelerometer

The habituation of human sleep to a noisy environment was investigated by p olysomnography (PSC), a wrist activity device (Actiwatch (R)), subjective e valuation and a performance test on the following morning. Eleven young mal e students slept for 17 nights in a sleep laboratory. PSG on the first, fou rth, fifth, ninth, 14th, and 17th nights was judged visually. Four of the s ubjects were continuously monitored by the wrist activity device. From the fifth to 14th nights, there was exposure to road traffic noise all-night lo ng, and consecutive experiments were conducted from the fifth to 17th night s. Agreement of sleep/wake assessment for Actiwatch (R) and PSG was 88.4%, on average, based on the data for 24 nights. Pearson's correlation coeffici ent of TST for Actiwatch (R) and sleep PSG was 0.848. Habituation to noise by wrist movement, sleep latency by PSG, and activity of mental muscles was not recognized. The association between wrist activity and mental muscle a ctivity was significant for three subjects out of four (r = 0.56, 0.81, 0.7 1, respectively). Percentages of positive wrist movement in each sleep stag e, such as the 3 + 4 stages, REM stage and stage MT, were compared with tho se in other stages. Wrist activity in Stage REM was significantly more freq uent than that in other stages for the three subjects. Wrist movement in St age MT was significantly more frequent than in other stages for the three s ubjects. REM latency, REM cycle, and five factors of subjective sleep, from the Oguri-Shirakawa-Azumi questionnaire (SQ), showed significant differenc es by analysis of variance for repeated measurements. When change from the 4th night was checked, sleepiness, worry, integrated sleep feeling and slee p initiation by SQ showed habituation of sleep to noise. Namely, sleep qual ity recovered to he level on a silent night by the fifth noisy night during the experiment. There is thus a habituation of sleep to noise when a subje ctive evaluation of sleep, such as the SQ, is used. (C) 2001 Academic Press .