Our population was composed of part of the individuals recruited as an independent sample aiming to validate the Spanish version of the SATED questionnaire . The participants were older than 18 years of age and considered to be physically and mentally able to participate in the study. The original sample was stratified by sex, age, educational and socioeconomic level to properly represent the general population (for a detailed description, see ). This study was approved by the Clinical Research Ethics Committee of the Arnau de Vilanova University Hospital in Lleida (CEIC-1694) and conducted according to the principles outlined by the Declaration of Helsinki.
The population was first recruited in 2017 as an independent sample to validate the Spanish version of the SATED questionnaire  (Fig. 1). Clinical and sociodemographic data were collected, and the participants completed the PSQI, ESS, SATED, and POMS questionnaires. During the COVID-19 outbreak in Spain, the individuals were contacted by their electronic addresses and asked to complete the previously answered questionnaires. The survey was available for a limited time window (from April 28 to May 12, 2020), and we obtained the answer from 71 individuals. Clinical and sociodemographic data were collected again due to possible changes over the years.
Clinical and sociodemographic variables
The following variables were collected: age, sex, educational level, work schedule, physical activity, previous diseases, medication intake, alcohol consumption, smoking, and caffeine-based drinks ingestion. Body mass index (BMI) was calculated as body weight (in kg)/height (in m2).
Pittsburgh Sleep Quality Index (PSQI)
Sleep quality was assessed by the PSQI . The questionnaire was composed of 19 questions representing one of the seven components of sleep quality: subjective sleep quality, sleep latency, sleep duration, sleep efficiency, sleep disturbance, sleep medication intake, and daytime dysfunction. Each component score was rated on a three-point scale, leading to a sum of up to 21 points. A PSQI score >5 indicated poor sleep quality, whereas a PSQI score ≤5 indicated good sleep quality.
Modified Epworth Sleepiness Scale (ESS)
Excessive daytime somnolence was assessed by the ESS . The questionnaire is originally composed of 8 questions to assess the chance of falling asleep during different daily situations. Three questions that were considered inappropriate due to the restrictive measures were excluded. Each question was rated on a three-point scale, in which 0 represented no chance of occurrence, and 3 indicated a high chance of occurrence. The overall score ranged from 0 to 15 points. Higher scores represented increased daytime somnolence.
Satisfaction Alertness Timing Efficiency Duration (SATED)
Sleep health was further assessed by the SATED . The questionnaire was composed of 5 questions representing one of the 5 following sleep-related dimensions: subjective satisfaction, alertness during waking hours, appropriate timing, efficiency, and duration. Each question was rated on a two-point scale, leading to a sum of up to 10 points. Higher scores indicated better sleep health.
Profile of Mood States (POMS)
The mood was assessed by the POMS . The questionnaire was composed of 28 questions representing one of the 5 following dimensions: tension (5 questions), depression (6 questions), anger (7 questions), vigor (6 questions), and fatigue (4 questions). Each question was rated on a five-point scale, with 0 representing ‘not at all’ and 4 indicating ‘extremely’. The score of each dimension was the sum of the given rates for each of the corresponding questions. The positive subscale corresponded to ‘vigor’, and the negative subscale was the sum of tension, depression, anger, and fatigue. The total score was calculated by subtracting the positive subscale from the total of the negative subscale (+100, to avoid negative values). Thus, higher scores indicated a negative mood.
The means (standard deviation, SD) were estimated for quantitative variables, and the absolute and relative frequencies were used for qualitative variables. We compared the questionnaires outcomes between both periods (pre- and during COVID-19 outbreak) using t-test or Wilcoxon rank sum test for paired samples. Furthermore, the relationship between POMS and PSQI scores during the COVID-19 outbreak was assessed through Spearman’s rank correlation coefficient. Finally, the differences in the PSQI components according to the working condition were assessed by linear models. All statistical analyses and data processing procedures were performed using R software, version 3.5.2 (Vienna, Austria).