Underestimation of nocturnal sleep duration in central disorders of hypersomnolence: an underrecognized feature?

Sleep misperception is well-documented in insomnia but remains understudied in central disorders of hypersomnolence (CDH). This study aimed to examine 1) total sleep time (TST) misperception in CDH and healthy controls, 2) the prevalence of accurate estimators, underestimators, and overestimators, and 3) the relationship between misperception and polysomnography (PSG) fragmentation variables. We included 420 adults with CDH (38 narcolepsy type 1-NT1, 52 narcolepsy type 2-NT2, 192 idiopathic hypersomnia-IH, 138 non-specified hypersomnia-NSH) and 86 healthy controls te0sted in Montreal, Canada. A replication cohort from a National Reference Center in France (n = 182; 79 NT1, 13 NT2, 35 IH, 55 NSH) was also analyzed. Participants underwent full-night PSGs, multiple sleep latency tests, and clinical interviews. TST misperception was defined as the ratio between self-reported to objective TST. Group comparisons were performed using ANCOVA adjusting for age and sex, and chi-square tests. Partial correlations were conducted to explore relationships between sleep fragmentation and TST misperception. In the Canadian cohort, all CDH subgroups underestimated their TST relative to controls (p < 0.001). The highest underestimation rates occurred in NT1 (44.7%) and IH (26.6%), while the lowest was observed in healthy controls (11.6%). The French cohort confirmed the absence of significant differences in TST misperception between CDH subgroups. No correlations were found between PSG fragmentation variables and TST misperception. Underestimation of nocturnal TST is common in adults with CDH and may complicate clinical assessment. These findings underscore the importance of integrating objective sleep measures when evaluating patients with hypersomnolence.