Patients with narcolepsy, especially narcolepsy type 1 (with cataplexy), have poorer nighttime sleep, the study researchers found in a systematic review and meta-analysis of studies on polysomnography (PSG)-measured nighttime sleep changes in these patients.
The study authors included 65 case-control studies that compared narcolepsy patients with healthy controls (HCs) that reported differences in PSG-measured nighttime sleep parameters between the groups. They also included 41 studies comparing patients of narcolepsy type 1(NT1) and type 2 (NT2), narcolepsy patients with and without rapid eye movement sleep behavior disorder (RBD)(n=4), and those positive or negative for human leukocyte antigen (HLA) DQB1*06:02 (n=3).
Compared with healthy controls, narcolepsy patients had significantly higher total sleep time (TST), wake time after sleep onset (WASO) (SMD = 0.670), awakenings numbers (AWN) (SMD = 1.501), stage shift (SS) (SMD = 0.937), apnea hypopnea index (AHI) (SMD = 0.253), periodic limb movement index (PLMI) (SMD = 1.032), and N1 percentage (SMD = 1.136).
Narcolepsy patients had significantly decreased sleep latency (SL) (standardized mean difference (SMD) = -0.954), sleep efficiency (SE) (SMD = -0.250), N2 percentage (SMD = -0.811), slow wave sleep (SWS) percentage (SMD = -0.230,), rapid eye movement sleep latency (REML) (SMD = -1.320) compared with healthy controls.
Publication bias was detected for the differences in TST (initially found to not have significant difference), SL, N1, SWS, REML, and PLMI between groups. After adjusting for publication bias, the study researchers identified a statistically significant increase in TST (SMD = 0.236) in narcolepsy patients compared with HCs while direction of change for the other measures remained consistent.
Meta-analysis revealed significantly decreased cyclic alternating pattern (CAP) rate (SMD = -1.115), A1 index (SMD = -1.022), A1 percentage (SMD = -0.446), and A2 index (SMD = -0.431) in narcolepsy patients compared with HCs.
Moderator analysis indicated that increased percentage of male narcolepsy patients in studies was significantly associated with decreased AWN (Point estimate=-2.496, P =.003) compared with HCs. Decreased mean age was significantly associated with AWN (Point estimate=-0.023, P =.031) and WASO (Point estimate=-0.022, P =.019) in narcolepsy patients compared with HCs.
Subgroup analysis, after running Egger’s test, found significantly decreased TST, SL, SE, REM percentage, and REML, and significantly increased WASO, AWN, SS, AHI, and PLMI in NT1 patients compared with NT2 patients.
Meta-regression analysis also revealed that decreased mean age across different studies was significantly associated with increased AWN (Point estimate=-0.023, P =.031) and WASO (Point estimate=-0.022, P =.019) in narcolepsy patients compared with HCs. A supplementary subgroup analysis also revealed that the magnitudes of increased AWN (SMD = 1.855) and WASO (SMD = 1.174) in children and adolescent narcolepsy patients (compared with HCs) were more obvious compared with those (AWN, SMD = 1.288; WASO, SMD = 0.547) in adult narcolepsy patients.
The study researchers also found a statistically significant increase in TST in narcolepsy patients compared with HCs in studies excluding patients taking psychoactive medications. Narcolepsy patients showed significant decrease in REML compared with HCs, which was more obvious in studies excluding patients taking psychoactive medications.
Limitations of the review included the inability to explore the effects of different psychiatric diseases or medications on PSG changes in narcolepsy and the exclusion of studies that used “clinical controls.”
Zhang Y, Ren R, Yang L, et al. Polysomnographic nighttime features of narcolepsy: A systematic review and meta-analysis. Sleep Medicine Reviews. Published online April 5, 2021. doi: 10.1016/j.smrv.2021.101488