Background: The validity of sleep quality and quantity indices as reported by schoolchildren has not been established. The purpose of this study is to evaluate the relationship between subjective sleep habits estimation and objective measurement data in schoolchildren. Methods: The study consisted of 42 healthy, junior high school children aged 13-14. Sleep log information was gathered over 7 consecutive days, using a sleep- monitoring device (Actiwatch®) and a questionnaire which covered the following aspects for sleep quality and quantity: bed time, sleep latency, sleep start, sleep end, wake up and assumed sleep length. The means of the sleep indices for 5 weekdays were used for analysis. Pearson's correlation coefficients and paired t-tests were used to evaluate the correlation and difference between subjective and objective sleep parameters. Results: The correlation coefficient between subjective and objective records was 0.49 (p<0.001) for sleep latency, 0.99 (p<0.001) for sleep start time, 0.99 (p<0.001) for sleep end time, and 0.97 (p<0.001) for assumed sleep length. The difference between subjective and objective records was 7.67 min (95% confidence interval [Cl]: 4.64-10.71) for sleep latency, and 0:02 min (95% Cl: -0:.01-0.05) for sleep start time, 0:02 min (95% Cl: 0:01 -0:03) for sleep end time, and 8.19 min (95% Cl: 4.93-11.45) for assumed sleep length. Conclusions: Although children tended to overestimate sleeping hours, the correlation between subjective and objective sleep indices except sleep latency was quite high. Thus, children's sleep questionnaire can be applied to surveys for sleep habits screening.
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