To compare cortisol levels, diurnal cycles of cortisol, and reactivity of cortisol to psychological stress in fibromyalgia (FM) and rheumatoid arthritis (RA) patients in their natural environment, and to examine the effect on results of accounting for differences among the groups in psychological stress and other lifestyle and psychosocial variables.
Participants were 21 FM patients, 18 RA patients, and 22 healthy controls. Participants engaged in normal daily activities were signaled with a preprogrammed wristwatch alarm to complete a diary (assessing psychosocial- and lifestyle-related variables) or provide a saliva sample (for cortisol assessment). Participants were signaled to provide 6 diary reports and 6 saliva samples on each of two days. Reports of sleep quality and sleep duration were also made upon awakening.
FM and RA patients had higher average cortisol levels than controls; however, there were no differences between the groups in diurnal cycles of cortisol or reactivity to psychological stress. While the groups differed on stress measures, surprisingly, the patient groups reported less stress. Furthermore, statistically accounting for psychosocial- and lifestyle-related differences between the groups did not change the cortisol findings.
The results provide additional evidence of hypothalamic-pituitary-adrenal axis disturbance in FM and RA patients. While such elevations are consistent with other studies of chronically stressed groups, the elevations in cortisol in this study did not appear to be due to ongoing daily stress, and there was no evidence of disturbed cortisol reactivity to acute stressors.