Publications (7)12.69 Total impact

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    ABSTRACT: Habituation of sleep to a ship's noise was assessed by actigraphy and a sleep questionnaire. Four male students aged 21–24 years were studied for 15 consecutive nights in an experimental bedroom. During the first four nights, the subjects slept in a quiet environment. For the next eight consecutive nights, the subjects were exposed to the noise of a ship's engine with a sound level of 60dB(A) (the International Maritime Organization Standard) previously tape-recorded in a room of a diesel engine ship. On the last three experimental nights, the subjects again slept in a quiet environment. The subjects went to bed in the experimental room at about 0:00 and were woken at 8:00 a.m. the next morning by an alarm clock. Sleep was monitored by a wrist-worn actigraphy. On the morning following each experimental night, the subjects were instructed to answer the OSA questionnaire, a structured self-rating sleep scale developed in Japan. Habituation of sleep to the noise of a ship with a sound level of 60dB(A) was observed to some extent in the subjective sleep parameters but not in the sleep parameters measured by actigraphy.
    Journal of Sound and Vibration 02/2002; 250(1):107-113. DOI:10.1006/jsvi.2001.3900 · 1.81 Impact Factor
  • T. Kawada · M. Kuroiwa · Y. Sasazawa · S. Suzuki · Y. Tamura ·
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    ABSTRACT: The authors conducted sleep time monitoring using an activity-detecting device on a married couple. The subjects were a 39-year-old man and a 36-year-old woman. They were continuously monitored for 1 year or a half-year from 1998 to 1999. Their daily activities were not limited. The male works in an office 5 days a week and stays at home on weekends. The female is a farmer and works in the field when the weather is clear. They usually went to bed at 10–11 p.m. and got up around 6 a.m. the next morning on weekdays. The activity-monitoring device, Actiwatch®, was installed on the wrists of their non-dominant arms. The number of body movements was calculated by the summation of the active electricity number. There was no significant monthly difference in the mean nightly total sleep time (TST) by analysis of variance in either the husband or the wife. When nocturnal and diurnal sleep were combined for the analysis, the mean value in April or May, 1999, was significantly larger than the values in July, August, December or October, although only in the husband. The sleep time for Saturday or Sunday was significantly extended as compared to that of a weekday. Power spectrum analysis showed the TST cycle to predominate on all 7 days in the week in both subjects.
    Journal of Sound and Vibration 02/2002; 250(1):75-82. DOI:10.1006/jsvi.2001.3904 · 1.81 Impact Factor
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    ABSTRACT: This study was designed to assess the effects of road traffic noise and frogs' croaking on the objective and subjective quality of sleep in a laboratory. The subjects were seven male students aged 19–21 years. They were exposed to recorded road traffic noise and frogs' croaking, with 49·6 and 49·5 dB(A)LAeq , and 71·2 and 56·1 dB(A) LAmax, respectively. The background noise in the experimental room was 31·0 dB(A) LAeq. The sleep EEG was recorded according to standard methods. The sleep polygraphic parameters examined were the percentage of sleep stage relative to the total sleep time (%S1, %S2, %S(3+4), %SREM, %MT), total sleep time, sleep onset latency, and awakening during sleep in minutes and sleep efficiency. A structured sleep rating questionnaire (OSA), was administered to the subjects after they awakened. The %S2 increased and the %SREM decreased during exposure to road traffic noise. However, no significant effect of exposure to frogs' croaking was observed on any of the polygraphic sleep parameters. The subjective quality of sleep was degraded more by exposure to road traffic noise than that to frogs' croaking.
    Journal of Sound and Vibration 02/2002; 250(1-250):91-99. DOI:10.1006/jsvi.2001.3902 · 1.81 Impact Factor
  • M. Kuroiwa · P. Xin · S. Suzuki · Y. Sasazawa · T. Kawada · Y. Tamura ·
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    ABSTRACT: The habituation of sleep to road traffic noise was investigated. Habituation of sleep is improvement of sleep quality. Nine male students aged 19–21 were exposed to tape-recorded road traffic noise ofLeq 49·6 dB(A) in an experimental bedroom. Among 17 nights, the first four and the last three nights were non-exposure nights and the other consecutive 10 were exposure nights. The polygraphic sleep parameters were: sleep stages S1, S2, S(3+4), rapid eye movements (REM), and so on. Subjective sleep quality was assessed by five scales of a self-rating sleep questionnaire named the OSA, sleepiness (F1), sleep maintenance (F2), worry (F3), integrated sleep feeling (F4), and sleep initiation (F5). In this experiment, the habituation of sleep to road traffic noise was observed clearly in all of the subjective sleep parameters of the OSA, though all of the polygraphic sleep parameters showed little or no evidence of habituation. This suggests that habituation to noise has two aspects, sensation and perception mechanisms, corresponding to sleep polygraphy and to questionnaire respectively.
    Journal of Sound and Vibration 02/2002; 250(1):101-106. DOI:10.1006/jsvi.2001.3901 · 1.81 Impact Factor
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    ABSTRACT: The habituation of human sleep to a noisy environment was investigated by polysomnography (PSG), a wrist activity device (Actiwatch®), subjective evaluation and a performance test on the following morning. Eleven young male students slept for 17 nights in a sleep laboratory. PSG on the first, fourth, fifth, ninth, 14th, and 17th nights was judged visually. Four of the subjects were continuously monitored by the wrist activity device. From the fifth to 14th nights, there was exposure to road traffic noise all-night long, and consecutive experiments were conducted from the fifth to 17th nights. Agreement of sleep/wake assessment for Actiwatch®and PSG was 88·4%, on average, based on the data for 24 nights. Pearson's correlation coefficient of TST for Actiwatch®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 activity was significant for three subjects out of four (r=0·56, 0·81, 0·71, respectively). Percentages of positive wrist movement in each sleep stage, such as the 3+4 stages, REM stage and stage MT, were compared with those in other stages. Wrist activity in Stage REM was significantly more frequent than that in other stages for the three subjects. Wrist movement in Stage MT was significantly more frequent than in other stages for the three subjects. REM latency, REM cycle, and five factors of subjective sleep, from the Oguri–Shirakawa–Azumi questionnaire (SQ), showed significant differences by analysis of variance for repeated measurements. When change from the 4th night was checked, sleepiness, worry, integrated sleep feeling and sleep initiation by SQ showed habituation of sleep to noise. Namely, sleep quality recovered to the level on a silent night by the fifth noisy night during the experiment. There is thus a habituation of sleep to noise when a subjective evaluation of sleep, such as the SQ, is used.
    Journal of Sound and Vibration 04/2001; 242(1-242):169-178. DOI:10.1006/jsvi.2000.3344 · 1.81 Impact Factor
  • Y. Tamura · T. Kawada · Y. Sasazawa ·
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    ABSTRACT: The effects of a steady sound level of 65 dB(A) from a diesel ship engine on nocturnal sleep were studied using polygraphic and subjective sleep parameters. Three healthy men, aged 29 to 33 years, participated in the experiment. Sleep polygrams and the sound level in a sleep laboratory were recorded for each subject for five exposure nights and five control nights. The following morning, the subjects answered a self-rating sleep questionnaire (called the OSA) and underwent simple reaction time tests. The percentage of S2, SREM latency and the REM interval increased, while %SREM decreased during the noise-exposed nights as compared with corresponding values on the control nights. Other parameters of sleep EEG were unchanged. Five scale scores for OSA, sleepiness, sleep maintenance, worry, integrated sleep feeling and sleep initiation deteriorated significantly on the noise-exposed nights as compared with the control nights. Canonical discriminant analysis was conducted using 19 sleep parameters. The standard partial regression coefficients of %SREM, %S2 and %S1 were somewhat higher than other parameters. It was suggested that exposure to the 65 dB(A) ship noise exerted adverse effects on nocturnal sleep, subjectively and in part polygraphically (REM sleep and shallow sleep).
    Journal of Sound and Vibration 08/1997; 205(4):417-425. DOI:10.1006/jsvi.1997.1007 · 1.81 Impact Factor
  • S. Suzuki · T. Kawada · Y. Kiryu · Y. Sasazawa · Y. Tamura ·
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    ABSTRACT: Twelve subjects were exposed to the noise of passing trucks at peak levels of 45, 50, 55 and 60 dB(A) for 15 min intervals throughout the night each for seven to 12 nights. Effects of the noise were observed by sleep electroencephalography (EEG). Three EEG parameters were affected by the noise event during stage 2. The number of spindles per epoch was depressed on average from 1·78 to 1·02 spindles per epoch or to 57% by the noise event of 60 dB(A), which lasted for only one minute. The threshold level for inducing the decrease was 32 dB(A), as assessed by a regression equation. Time % delta wave was depressed for six minutes, with a threshold level of 41 dB(A). The integral EMG increased in response to the noise event for one minute, and the threshold level for the integral EMG was 34 dB(A).
    Journal of Sound and Vibration 08/1997; 205(4):411-415. DOI:10.1006/jsvi.1997.1006 · 1.81 Impact Factor