Determination of the Role of Subjective Investigation Methods in Assessment of Measures of Sleep Quality

Objectives. To assess the accuracy of questions for determining the quality and duration of sleep. Materials and methods. An in-depth study was performed with assessment of sleep parameters in 136 patients, 49 of these undergoing polysomnographic (PSG) investigations. Subjectively, sleep was assessed using the Sleep Quality Questionnaire and the Pittsburgh Sleep Quality Index; objective assessments were obtained from PSG recordings. Results. Sleep quality in the laboratory was assessed as “Worse than at home” by one third of respondents. Sleep duration in this group was 1.5 h shorter than in the group assessing sleep in the laboratory as “Just as good at home.” Despite this, most respondents slept longer in the laboratory than they had averaged over the preceding month. Overall sleep evaluation showed that 59% of respondents noted sleep disturbance. Nocturnal sleep duration by PSG data was 6.6 [3; 9] h, compared with self-assessments of 7 [3; 10] h ( p = 0.06); average sleep duration was 8 [5; 10] h ( p = 0.005); assessments over the last month gave 7 [5; 9] h. Conclusions. Assessment of sleep quality in the laboratory as “worse than at home” was linked with subjectively shorter sleep durations. Subjective assessment of sleep duration and the time of falling asleep the evening before were quite accurate, in contrast to subjective assessments of the number of nocturnal wakings. Assessment of mean sleep duration depended on how the question was formulated.