Our survey of Japanese nurses working in inpatient wards for COVID-19 patients found that COVID-19-related occupational stress, physical symptoms, and psychological distress were high during the peak period of the first wave, then decreased after the peak had passed. Correlations were found between COVID-19-related occupational stress and psychological distress, and between psychological distress and physical symptoms during the peak period, but not two months after the peak. Notably, increased workload and insomnia were associated with psychological distress regardless of the peak or post-peak period, and increased workload was also associated with physical symptoms during the peak period. The present study is the first Japanese report to show an interrelation between COVID-19-related occupational stress, psychological distress, and physical symptoms.
Changes in COVID-19-related occupational stress, psychological distress, and physical symptoms
Previous studies have reported occupational stress, such as increased workload, fear of infection, physical symptoms such as pain and insomnia, and psychological distress among HCWs during the COVID-19 pandemic. (7, 9, 13) Their results were confirmed for Japanese HCWs in the present study. In addition, our finding that COVID-19-related occupational stress, psychological distress, and physical symptoms during the peak period were improved two months after the peak suggests that some of these mental health problems are reversible. However, if the outbreak is repeated in future waves and the period of engagement is prolonged, the results might be different. Future cross-sectional follow-up studies on changes during and after repeated waves will be important.
Prevalence of physical symptoms and their changes
Among the somatic symptoms, the prevalence of insomnia (56.3%) in our study was higher than that seen in in previous reports, which ranged from 21–39.3%. (7, 9, 13) This difference may be related to the high prevalence of insomnia reported in Japan and the exacerbation of insomnia due to the increased workload, as discussed below. Furihata reported that 41.4% of female hospital nurses in Japan presented short sleep duration, less than six hours. (14) Because of the high prevalence of insomnia in Japanese healthcare workers, programs should be implemented to follow them carefully and to provide intervention where necessary.
Interrelation between occupational stress, psychological distress, and physical symptoms
We revealed for the first time an association between COVID-19-related stress and physical symptoms among Japanese healthcare workers treating COVID-19 during the peak infection period. A previous report showed that occupational stressors (nursing workload and fear of infection) were associated with high risk of anxiety and depressive symptoms (15). An association between occupational stress and psychological distress was also found in the present study, however, there was no association between anxiety about infection and physical symptoms related to COVID-19. These differences may be due to differences in the subjects and/or questionnaires.
Previous studies have reported that appetite loss was correlated with depression and anxiety. (7) In the current study, the total score of physical symptoms (gastrointestinal symptoms, pain, appetite loss and insomnia) was positively correlated with K6. This result suggests that it is necessary not only to pay attention to psychological distress but also to these physical symptoms during future waves of this or other infectious events. Although the post-peak OS, PS, and K6 scores were not correlated, it is possible that the decrease in the values of OS, PS, and K6 scores might be related to these results.
Possible interrelations were analyzed with respect to increased workload and fear of infection in OS and for pain and insomnia in PS. The results showed increased workload and insomnia to be associated with psychological distress regardless of peak or post-peak period and that increased workload was associated with insomnia both during and after the peak period. It has been reported that "few non-work days" is a risk factor for increased PHQ-9 (Patient Health Questionnaire-9; self-administered depression scale) scores among Japanese hospital workers treating COVID-19 (16). Therefore, the increased workload and fewer non-work days may have caused exacerbation of psychological distress such as depression and physical symptoms including insomnia in Japanese medical personnel during the peak period.
Pain was not associated with K6 in either the peak or post-peak period, which is incompatible with our hypothesis on pain. From the perspective of conceivable courses of pain, because it might take a longer time for pain to become symptomatic, future longitudinal studies will needed to clarify the association with pain.
Previous reports and our present results suggest that to reduce psychological distress during the peak periods of the COVID-19 outbreak, it is important to reduce COVID-19-related occupational stress, especially to prevent an increase in workload and not to reduce non-work days. Of the physical symptoms, it is important to pay careful attention to insomnia.
There are several limitations to our study. First, the number of participants was small. Therefore, we are currently conducting a prospective study with a larger number of participants. Also, the present study lacks data on baseline values, including history of physical symptoms. However, because OS, PS, and K6 scores all declined after the peak, it is thought that the baseline scores would be similar to or lower than the post-peak scores. Furthermore, we used retrospective questionnaires in part of the study, which has the problem of recall bias. This issue needs to be addressed in future prospective studies. Finally, the participants were overwhelmingly female, however, the proportion is similar to the overall proportion of nurses in Japan (7.8% males) (Report on Public Health Administration and Services in Japan, 2018). Therefore, we considered the study to be representative of the nurses working in COVID-19 wards in Japan.