This cross-sectional study was conducted from February 18 to March 1, 2020. Data was collected from five provinces (Hubei, Guangdong, Sichuan, Jiangsu and Gansu) which were purposely selected to cover different levels of epidemic severity defined by numbers of reported cases (by March 5, 2020, 67466, 1351, 539, 631, and 102 COVID-19 cases were reported in the selected five provinces, respectively), and to cover different regions of China (center, southern, western, eastern, and northern). In each province, 3-5 cities were selected; within selected cities, 3-5 districts/counties and 5-10 subdistricts/towns were further selected using similar methods to represent both different levels of the outbreak and to represent different regions. At province, city and district/county levels, CDCs workers were investigated, and at subdistrict/town level, PHI workers were investigated. We targeted at least 5000 public health workers, with a ratio of CDC/PHI workers of around 1/2.
Eligible participants were: 1) aged 18 years old or above; 2) working at CDC or PHI of the selected places during the study period; 3) participated in COVID-19 control and prevention-related work. Site investigators (e.g., CDC workers) of each province distributed the survey link through their Wechat/QQ working groups. Wechat and QQ are popular communication/social networking mobile-phone applications used in China that are ubiquitous in workplace settings. All participants were informed of the background, aims, anonymous nature and length (about 8-12 minutes to complete) of the survey. They were also informed that completing the questionnaire signified their informed consent. No compensation was provided to the participants. The study was approved by the ethics committee of the School of Public Health, Sun Yat-sen University (Reference no.: 2020-012).
Information about age, sex, job title, and whether they have children under 6 years old (i.e., the school age) were collected. Participants’ areas of routine work before COVID-19 outbreak were collected in Guangdong Province. We only collected this information in Guangdong province, and it was deleted in other provinces after feedback from the pilot trial in Guangdong that the questionnaire was too long.
COVID-19 control and prevention work-related variables.
We collected information from all participants about their work in terms of work contents, readiness for the work, and time of starting the work. Detailed variables included are listed below.
1) work contents. The preset list of work contents included 14 fieldwork questions covering for example face-to-face epidemiological investigation of the patients/close contacts, epidemiological investigation by phone or video call, medical observation of the close contacts, specimen collection and shipment, health education, and community-based investigation; and 11 non-field work topics covering for example preparation of technical guidelines, data analysis and report writing, laboratory test, comprehensive coordination and publicity, and technical training. Participants were asked to select work that they have been involved in from the preset list and fill in other contents that were not included on the list if any.
2) time spent in training on COVID-19, coded as none, 1-4 hours, 5-8 hours, 9-16 hours, and >16 hours.
3) knowledge of COVID-19 prevention and control, from 1 ‘adequate’ to 5 ‘very inadequate’.
4) Date the participant started COVID-19 prevention and control work. In data analysis, we use chose the cut-off date of January 23 because it is the date of closure of Wuhan city and also it is the day just before the Chinese New Year.
5) severity of the epidemic in their provinces, from 1 ‘very low’ to 5 ‘very high’ according to confirmed cases in each province.
Efforts and sacrifices.
Participants were asked about their efforts and sacrifices during the outbreak: 1) number of days that they have worked all night, 2) whether they have worked during the whole period of Chinese New Year, and 3) family sacrifices such as not going home or sending children to parents’ home, to avoid infecting family members.
Perceptions related to COVID-19 and work were also collected. One item was used to assess their concerns about being infected at work, from 1 ‘none’ to 5 ‘very worried’. One item was used to assess how long they can persist with their current work intensity, coded as 1-2 weeks, 3-4 weeks, 1-3 months, or >3 months.
Perceived support and perceived troubles at work were measured by self-constructed items which were developed after discussions with CDC and PHI workers and among the research team. The perceived support scale consisted of three items to measure perceived support from colleagues, family, and society rated on a Likert-type scale from 1 ‘none’ to 5 ‘very much’. The three items showed acceptable internal consistency in this study (Cronbach’s alpha = 0.760). Perceived troubles at work consisted of five items, which were rated on a 5-point Likert scale, from 1 ‘none’ to 5 ‘very much’. For example, participants were asked how often they have been treated unfairly at work. The Cronbach’s alpha for perceived troubles was 0.842 in this study.
Health outcomes included overall health status, depression, and anxiety. Overall health was measured by self-rated health status from 1 ‘very poor’ to 5 ‘very good’, which has been widely used globally and in China [28, 29]. The 9-item patient health questionnaire (PHQ-9) was used to assess the presence of depressive symptoms. The Chinese version of the PHQ-9 has been validated for the general population, showing good internal reliability . Participants were asked to rate how often they have experienced the depressive symptoms in the past two weeks, on a 4-point Likert scale, from 0 ‘none’ to 3 ‘nearly every day’. The total score ranges from 0 to 27, with a higher score reflecting greater severity. A score of ten or more was classified as a major depressive disorder. In this study, the Cronbach’s alpha value was 0.922.
The 7-item General Anxiety Disorder scale (GAD) was used to measure anxiety . Each item was rated on a 4-point Likert scale ranging from 0 ‘never’ to 3 ‘often (almost every day)’. The cutoff point of ten or above is used to define a probable case of moderate anxiety disorder. In this study, the Cronbach’s alpha value was 0.937.
Descriptive analysis was conducted to characterize the study. Chi-square tests, t-tests, and rank sum tests were used to investigate differences among CDC workers and PHI workers. To explore potential factors of the three health outcomes (i.e., self-rated health, depression, and anxiety), three sets of logistic regression models were performed in parallel. First, bivariate logistic regression analyses were used to examine the associations between all variables of interest and the three outcomes. Then adjusted logistic regression models were performed to identify the associations between COVID-19 related variables (COVID-19 control and prevention work related variables, efforts and sacrifices during the outbreak, perceptions) and the three outcomes, after controlling for potential confounders (sex, age, having children under 6 years and job title). In the final models, multivariate forward stepwise logistic regression models were fitted, using all COVID-19 related variables that were found to be significant in the univariate analysis as candidates for selection, with sociodemographic variables entered in the model. Unadjusted odds ratios (ORu) from univariate logistic regression models, adjusted odds ratios (AOR) from multiple logistic regression models, and their respective 95% confidence intervals (CIs) were reported. IBM SPSS Statistics 25 was used for data analysis. Significance referred to p value <.05.