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Relation between daily rest periods and sleep quality (Pittsburgh Sleep Quality Index (PSQI-J) score). The mean PSQI-J score is an estimated marginal value that is adjusted for sex, age, industry type, smoking status, and alcohol frequency. The error bars indicate the standard error. aThe cutoff point for primary insomnia was ≥6.0. The 13 h DRP group was not over the cutoff point.
