As a retrospective study, there were no objective tools for sleep assessment in patients with COVID-19. The RCSQ is empirically valid and the most widely used subjective survey instrument for assessing the quality of ICU patients' sleep (Nagatomo et al., 2020, Richards et al., 2000, Simons et al., 2018). In a clinical study of 70 ICU patients, the RCSQ was validated against polysomnography (PSG) (Richards et al., 2000), which is considered the gold standard method for evaluating sleep. We chose the RCSQ for assessing the sleep quality of patients with COVID-19 in non-ICU wards, since the frequent shifting of duty during ward-rounds, and the isolated environment without family member' companion in non-ICU ward for patients with COVID-19, are similar to that in the ICU wards for patients who are recovering from critical illness. Since not all patients were able to accurately recollect and assess their daily sleep quality during their hospitalization, we broadened the application scope of the RCSQ and only assessed the overall sleep quality within the first week, second week, and third week after hospital admission. In order to minimize different forms of bias, including recollection and response bias, patients with COVID-19 who were unsure of their sleep quality were excluded from the study. We also lowered the upper limit of the RCSQ score that defines poor-sleep quality (≤50) to minimize bias, while the cut-off point differentiating good and poor sleep was 70/100 in previous studies (Mannion et al., 2019, McKinley et al., 2013). Patients with at least two RCSQ scores of 50–70 were also excluded. After assessment with the RCSQ, overall sleep quality was further confirmed using the Chinese version of the PSQI, which has been shown to be reliable and valid for the Chinese population (Liu et al., 1996). The PSQI could discriminate between poor and good sleep quality over the preceding 30-days and has been widely used in clinical and non-clinical settings (Mollayeva et al., 2016). In our study, we used both the RCSQ and the PSQI to better reflect the subjective sleep quality of patients with COVID-19 during hospitalization. Furthermore, patients were excluded in cases of inconsistency between the RCSQ and PSQI scores. In addition, after patients' self-reported sleep assessment, we further checked patients' overall sleep quality by asking their hospital roommates, as well as the doctors and nurses responsible for their treatment.