In Brief:
This is the largest study to date comprising 2540 community-based participants with polysomnographic data, examining sleep underestimation and overestimation in relation to quality of life. More than one-third of participants estimated their sleeping time significantly more or less than the objective polysomnographic sleeping time. These sleep underestimators and overestimators, compared with normoestimators, reported a poor quality of life (physical and mental aspects), suggesting a substantial prevalence and mental health comorbidity of subjective-objective discrepancy in sleep.