Chain mediating effect of somatic pain and sleep duration between chronic disease count and depressive symptoms in older adults.

Sleep is an essential physiological activity for humans (). In recent decades, lifestyle changes related to societal trends and economic development have been coupled with an increase in the prevalence of sleep disorders. Sleep disorders negatively impact physical, psychological, emotional, and social functioning, and are common among all age groups (, ). Healthcare personnel, and in particular hospital clinical staff, are essential workers who may be at increased risk of sleep disorders due to busy clinical workloads, shift work, and high mental pressure. Poor sleep quality and inadequate sleep among healthcare professionals negatively impact clinical safety and quality (, ). Frequent overtime and night shifts resulting in insufficient sleep may lead to adverse effects on physical health and increased risk of accidents (). Furthermore, frequent night shifts and lack of sleep among hospital clinical staff have been found to be risk factors associated with burnout (). The COVID pandemic placed unprecedented pressure on healthcare workers worldwide. In response to the public health threat posed by COVID, China imposed a broad array of strict prevention and control measures, including city-wide ‘lock-down’ restrictions on movement and rapid deployment of healthcare personnel to conduct mass nucleic acid testing and vaccination campaigns. Many healthcare workers spent long hours working in isolation wards and critical care units while facing the physical demands of wearing personal protective equipment and psychological challenges such as risk of infection, disruption of routine, and separation from loved ones and colleagues. The lifting of pandemic control measures in China in December 2022 was followed by a surge of COVID cases and hospitalizations through early 2023, necessitating hospital staff to work overtime while caring for many critically ill patients ().