People with advanced dementia have impaired immune function, impairments in cognition, and a decreased tolerance for physical, environmental, and psychosocial stressors.1,2 Because physical, environmental, and psychosocial stressors activate the hypothalamic-pituitary-adrenal (HPA) axis to increase the secretion of cortisol, alterations in HPA axis function may in turn have an impact on physical and emotional responses to stressors and further compromise physical and cognitive status.3 The purpose of this study was to describe the diurnal rhythm of cortisol in people with advanced dementia and examine differences in mean cortisol level, and the slope and pattern of the cortisol rhythm associated with cognition and illness burden.
The cortisol diurnal rhythm is robust and persists from infancy to old age.4,5 A typical diurnal rhythm of cortisol is characterized by a peak after waking followed by a decline in levels throughout the day.6 While the normal diurnal rhythm of cortisol is well-established, individual variability has been documented. Physical, environmental, and psychosocial factors have been associated with changes in cortisol diurnal pattern. Alterations have been found in disease states such as rheumatoid arthritis,7 depressive symptoms,8 Alzheimer’s disease,9–10 and fibromyalgia.11 Environmental and psychosocial factors associated with changes in diurnal rhythm include living in a circumpolar region,12 shift work,13 daily hassles,14 military survival training,15 and child maltreatment.16
Although most healthy older adults have normal circadian rhythms,5 dampened patterns were reported in 2% and 17% of two samples of community dwelling older adults.17,18 Dampened patterns were found in 69% of older adults with complaints of memory deficits and/or depressive symptoms.8 Flattening of the cycles usually occurs because of an elevated afternoon cortisol rather than a decreased morning cortisol.19,20 Fiocco et al. 8 found that 19% of 42 depressed participants had a typical negative slope on the first week of sampling, followed by a flattened pattern the next week.
Changes in cortisol pattern that reflect altered HPA axis activity may have deleterious effects on health outcomes.3,21 However, it is still unclear if cortisol level, slope, pattern or consistency of pattern has the most significant impact on health.21 Sephton, et al.22 found that a flatter cortisol slope was associated with an increased risk of mortality in a study of 104 women with metastatic breast cancer. Flatter cortisol slopes were associated with low counts and suppressed activity of circulating natural killer (NK) cells.