**2. Materials and Methods**

This cross-sectional study was conducted in the Western Pomerania region in Poland from 3 May 2020 to 17 May 2020. The study area was showing an incidence at 6/100.00 and prevalence at 31/100.00 during this period. This study included 6 hospitals with clinics or wards that diagnosed or hospitalized COVID-19 patients. In total, 723 people took part in the study. The study group consisted of 134 individuals with SLE. The control group consisted of 589 people without SLE. Each of the survey participants gave their informed consent by taking part in the survey. The participants could stop the survey at any time. The survey was anonymous and ensured the full confidentiality of information.

In this study, we focused on the symptoms of anxiety, depression, and sleep disorders in all participants using the 7-item Generalized Anxiety Disorder scale (GAD-7; range 0–21; no anxiety ≤ 4, anxiety > 4) [16] to assess the severity of anxiety, the 9-item Patient Health Questionnaire (PHQ-9; range 0–27; no depression ≤ 4, depression >4) [17–22] to assess the severity of depression symptoms, and the 7-item Insomnia Severity Index (ISI; range 0–28; no insomnia ≤ 8, insomnia > 8) to assess the severity of sleep disorder symptoms [23–26]. Cut-off points for anxiety, depression, and insomnia were established in accordance with the literature. Participants with scores below the cut-off points were characterized as showing no symptoms, while those who obtained scores above the cut-off points were characterized as showing symptoms.

Each participant gave basic demographic data, including their gender (male or female) and age. Data on coexisting diseases such as diabetes mellitus, hypertension, heart failure, coronary heart disease, chronic obstructive pulmonary disease, and dyslipidemia were also collected from each participant. Each participant was also asked about tobacco smoking.

The Pomeranian Medical University Ethics Committee approved the study protocol (KB-0012/26/04/2020/Z) which conformed to the ethical guidelines of the Declaration of Helsinki.
