Transient and all-night effects of passing truck noise on the number of sleep spindle.

Changes in the number of transient and all-night sleep spindles by traffic noise of 55 to 65 dB(A) were studied. The sleep parameters were the number of spindles per minute in stages 2, 3, and 4 (S2, S3, S4) and the total number of spindles divided by the total sleep time. A transient decrease in the number of spindles was recognized and after noise exposure, the number of spindles increased to near the pre-exposure level. Spindles were counted from S2, S3 and S4 for all-night sleep. The number of spindles in all-night sleep by noise exposure increased. The authors explain discrepancies in the results by a compensatory brain mechanism of sleep disturbance due to passing truck noise.