Effect of some factors on sleep polygraphic parameters and subjective evaluations of sleep

In this study a bedroom in a noisy area and one in a quiet area were used to investigate the effects of road traffic noise on sleep. Subjective sleep and objective sleep polygraphic parameters were obtained from subjects sleeping in each bedroom. Differences in these parameters at the two locations were compared. The experimental environment differed from those formerly used. The authors thus examined the influences on sleep of covariates in terms of subject differences, age differences, sex difference, differences in the order of experimental nights, set differences, and noise differences. From Spearman's rank correlation coefficient and two-way analysis of variance, subject and age differences were found to have greater effects on many sleep parameters than noise differences. Principal factor analysis was done for young and old subjects separately. The sixth factor was related to noise differences. The sleep parameter common to young and old subjects of the sixth factor was %REM.