[Analysis of the relations between polysomnographic data and subjective evaluation of sleep in a group of normal...

The aim of the present study was to analyse the relationships between polysomnographic variables and the subjective evaluation of sleep quality in a sample of healthy subjects. Thirty one healthy subjects (7 women, 24 men) aged 16 to 74 (mean = 33.8; standard-deviation = 15.6) were included in the study. After one accommodation night, sleep was recorded during three consecutive nights in the sleep laboratory. Subjective evaluation of sleep quality was assessed by a questionnaire including quantitative aspects as well as qualitative aspects of sleep. The data of the third night are analysed here. Two factor analyses were performed on the sleep questionnaire. Two factors were extracted; they were named "depth" and "rest". Using a stepwise multiple regression analysis, these two indices of sleep quality were tested for explanation by 24 polygraphic variables. The "depth" factor was revealed positively related to the first awakening latency, and negatively to sleep onset latency, Rapid Eye Movement latency and the number of awakenings. The "rest" factor was shown to be positively related to stage 1 duration and sleep onset latency, and negatively to stage 4 duration and the number of awakenings. Some of these relationships have already been described. Others seem surprising and may seem questionable. These results raise the question of the relations between objective measures of sleep, the polygraphic variables, and the subjective process of perceiving and evaluating sleep.