2.2. Data collection

All subjects completed an online questionnaire. Data collected included demographic characteristics, health status, workplace, lifestyle, attitude towards COVID-19 control, and assessments of anxiety, depression and sleep quality.

Legislators, senior officials, managers, (associate) professionals, technicians, and clerks were defined as white-collar workers according to the International standard classification of occupations (ISCO) [¹⁰]. Annual household income was classified into three groups: low income (0–50,000RMB), middle income (50,001–200,000RMB) and high income (>200,000RMB) in 2019. Smoking was defined as consuming at least one cigarette per day for at least six months [¹¹]. Alcohol drinking was defined as drinking any alcohol at least three times per week for at least six months [¹²]. Tea consumption was defined as drinking any tea at least three times per week for at least six months [¹³]. Regular physical exercise was defined as having physical exercise at least three times a week for at least 30 min each time [¹⁴]. The nine-item Patient Health Questionnaire (PHQ-9) was used to measure the depressive symptom with a summed score ranging from 0 to 27 for the nine items, and mild depression was defined as a PHQ-9 score≥5 in this study [¹⁵]. Cronbach's alpha for the internal consistency reliability and two-week test-retest reliability of the Chinese version of the PHQ-9 were 0.86 [¹⁶]. The seven-item Generalized Anxiety Disorder (GAD-7) was used to measure anxiety symptom with a summed score ranging from 0 to 21, and mild anxiety was defined as a GAD-7 score ≥5 in this study [¹⁷]. Cronbach's alpha for the internal consistency reliability of the Chinese version of the GAD-7 was 0.90 and the test-retest reliability was 0.86 [¹⁸].