Sleep quality worsened in an evening chronotype compared to others: a year-long longitudinal cohort study with prolonged lockdowns and restriction relaxations in RECETOX MU university employees

BackgroundIn 2020, people around the world were challenged by the outbreak of the COVID-19 pandemic. Countries responded with various restrictions, including lockdowns and stay-at-home orders, in an attempt to prevent the spread of the disease. Citizens were thus subjected to unprecedented uncertainty and stress. Prolonged exposure to such conditions may impact human health and well-being. One of the core aspects of proper physiological functioning is sleep. This prospective longitudinal study aims to investigate sleep quality and its relationship to chronotype over a year-long period from September 2020. Methods and findingsOur year-long longitudinal prospective study focused on an employee cohort (N=54) at the Research Centre for Toxic Compounds in the Environment (RECETOX) of Masaryk University in the Czech Republic. During the first half of this period, three lockdowns with a cumulative duration of 100 days were imposed. During the second half of this period, the imposed restrictions were relaxed. Individuals were measured quarterly, i.e. at five time points. Sleep quality was measured using the Pittsburgh Sleep Quality Index (PSQI) while chronotype was established using the Reduced Morningness-Eveningness Questionnaire (rMEQ). We also used Perceived Stress Scale (PSS-14), Beck Depression Inventory (BDI-II), and General Anxiety Disorder-7 (GAD-7) to address potential confounders. The response rates of valid measurements across time points ranged from 87.04 % to 61.11 %. Our results show that sleep quality significantly worsened across the year for the evening chronotype but improved for the neutral and early chronotypes. Overall, over the year the incidence of poor sleep decreased by 16.13 % with 95% CI [-6.10%; 37.16%]. We did not find any significant sex differences in sleep quality. Perceived stress, symptoms of anxiety and depression were positively significantly associated with sleep problems in all measurements except in June. This study is limited by the small sample, decreasing number of individuals in chronotype categories and the lack of information on napping behavior. ConclusionThese findings shed new light on the long-term influence of pandemic-related restrictions on individuals and particularly on the potentially more vulnerable evening chronotypes.