Social timing influences sleep quality in patients with sleep disorders

© 2020 Elsevier B.V. All rights reserved.Objectives: We aimed to compare three variants of the Pittsburgh Sleep Quality Index (PSQI usual, work- and work-free days: PSQIu, PSQIw, PSQIf) and to assess whether chronotype (MSFsc)/social jetlag (SJL) are associated with sleep quality in patients with sleep disorders (SD). Methods: In sum, 431 SD patients and 338 subjects from the general population (GP) were included. Participants filled in three variants of the PSQI and the Munich ChronoType Questionnaire (MCTQ). We used Generalized Estimating Equations (GEE) to investigate effects of group (GP, SD), PSQI (usual, work or free) and their interaction (group∗PSQI) on scores. To investigate associations between MSFsc/SJL and the difference between PSQIw and PSQIf (PSQIdiff) in patients with SD we used linear regressions (N = 352). We used Sobel to test whether there was a mediation effect of SJL on the association between MSFsc and PSQIdiff. Results: PSQI scores differed between groups (p < 0.001). Post-hoc analysis revealed a significant difference between PSQIu vs. PSQIf and PSQIw vs. PSQIf with PSQIf presenting lower scores, while PSQIu vs. PSQIw did not differ in any group. In line with previous findings, SJL was associated to PSQIdiff in SD patients. Conclusions: PSQIu mainly represents sleep quality on workdays also in SD patients. Being a late chronotype seems to be associated with higher differences in sleep quality on work-vs. free days mostly when it coincides with societal time constraints. Since sleep quality is poorer on workdays even in SD patients, we suggest that treatment strategies should address social aspects affecting sleep, including ways of minimizing SJL.This study was financed in part by the Fundação para a Ciência e Tecnologia (FCT) PhD research grant PDE/BDE/114584/2016, the Coordenaçao de Aperfeiçoamento de Pessoal de Nível Superior, Brasil (CAPES - PVE A046/2013) - Finance Code 001, and the Deutscher Akademischer Austauschdienst (CAPES/DAAD - PROBRAL 12/2017).