Sleep and Circadian Health of Critical Survivors: A 12-Month Follow-Up Study

Abstract

Objectives: To investigate the sleep and circadian health of critical survivors 12 months after hospital discharge and to evaluate a possible effect of the severity of the disease within this context.

Design: Observational, prospective study.

Setting: Single-center study.

Patients: Two hundred sixty patients admitted to the ICU due to severe acute respiratory syndrome coronavirus 2 infection.

Interventions: None.

Measurements and main results: The cohort was composed of 260 patients (69.2% males), with a median (quartile 1-quartile 3) age of 61.5 years (52.0-67.0 yr). The median length of ICU stay was 11.0 days (6.00-21.8 d), where 56.2% of the patients required invasive mechanical ventilation (IMV). The Pittsburgh Sleep Quality Index (PSQI) revealed that 43.1% of the cohort presented poor sleep quality 12 months after hospital discharge. Actigraphy data indicated an influence of the disease severity on the fragmentation of the circadian rest-activity rhythm at the 3- and 6-month follow-ups, which was no longer significant in the long term. Still, the length of the ICU stay and the duration of IMV predicted a higher fragmentation of the rhythm at the 12-month follow-up with effect sizes (95% CI) of 0.248 (0.078-0.418) and 0.182 (0.005-0.359), respectively. Relevant associations between the PSQI and the Hospital Anxiety and Depression Scale (rho = 0.55, anxiety; rho = 0.5, depression) as well as between the fragmentation of the rhythm and the diffusing lung capacity for carbon monoxide (rho = -0.35) were observed at this time point.

Conclusions: Our findings reveal a great prevalence of critical survivors presenting poor sleep quality 12 months after hospital discharge. Actigraphy data indicated the persistence of circadian alterations and a possible impact of the disease severity on the fragmentation of the circadian rest-activity rhythm, which was attenuated at the 12-month follow-up. This altogether highlights the relevance of considering the sleep and circadian health of critical survivors in the long term.

Figure 1.

Patients included in the objective evaluation of sleep and circadian rest-activity rhythm (actigraphy) over the three follow-up time points. A subgroup of patients was randomly selected at the 3-mo follow-up and later evaluated during the following visits, excepting those who were not willing to participate for a second and/or third time. Additional patients (who underwent the subjective but not the objective assessment at the 3-mo follow-up) were randomly selected for the objective evaluations at the following visits. (The figure was created with BioRender.com.)

Figure 2.

Evolution of sleep and circadian health along the 12-mo follow-up. Data are represented as median (quartile 1–quartile 3). The p value threshold defining statistical significance was set at less than 0.05. IMV = invasive mechanical ventilation, PSQI = Pittsburgh Sleep Quality Index.

Figure 3.

Baseline predictors of the Pittsburgh Sleep Quality Index (PSQI) score and actigraphy-related variables at the 12-mo follow-up. The forest plot demonstrates associations between baseline characteristics of the patients (obtained during the ICU stay) and the main outcomes at the 12-mo follow-up, in which right-sided representations indicate positive associations and left-sided representations indicate negative associations. Significant associations (p value threshold defining statistical significance was set at < 0.05) are those in which the lines do not cross the central line (effect size [95% CI] = 0). The generalized linear models were adjusted for age and sex (except for the sociodemographic and anthropometric data) after the standardization of continuous variables. BMI = body mass index, CFI = circadian function index, COPD = chronic obstructive pulmonary disease, IMV = invasive mechanical ventilation, NIMV = noninvasive mechanical ventilation.