General procedure
Cor, Cor II
The activity of the HPAA was assessed by measuring cortisol in saliva samples. Salivary cortisol was preferred due to its practicability in sample collection, which is less invasive and requires less effort from participant compared to other methodsDiurnal cortisol data were obtained using Salivette® tubes (Sarstedt™, Leicester) containing an untreated cotton swab. Four saliva samples were collected from participants on a typical ward routine day. The participants were all inpatients on the same ward with identical routines. Participants were instructed to chew on the saliva collectors after awakening (Cor I), 30 min after getting up (Cor II), 8 h after awakening (Cor III), and 14 h after awakening (Cor IV), while still in bed. Additional instructions were provided by ward health workers (i.e., nurses, postgraduate trainees or interns) regarding precautions related to meals, drinks, teeth brushing, and smoking. The ward health workers also recorded the date and time of sampling and placed the tubes with saliva samples in the refrigerator. All samples were stored at – 25 °C, and after thawing, they were centrifuged for 5 min at 3000 rpm, resulting in a clear supernatant of low viscosity. Salivary cortisol levels were measured using a time-resolved immunoassay with fluorescence detection