Twenty-four-hour urinary free cortisol levels in vascular dementia and in Alzheimer's disease

During senescence, homeostatic and stress-response capacities are impaired, particularly in patients with dementia. Therefore, the study of the hypothalamic-pituitary-adrenal (HPA) axis function, assuring the physiological adaptation to the environmental stimuli, appears to be relevant. In this study we compared the 24-hour urinary free cortisol in patients with Alzheimer's disease (AD), and with vascular dementia (VD). The AD patients were 15, mean age 70 ± 8 years (8 males and 7 females), the VD patients were also 15, mean age 71 ± 9 years (11 males and 4 females), and we studied also 23 normal control subjects (C), mean age 68 ± 9 years (15 males and 8 females). VD and AD were diagnosed according to the DSM-IV criteria. Subjects under drug treatment, with depression or with illness which could influence HPA axis function, were not included. In all subjects, clinical history, psychometric examination, computerized cerebral axial tomography were performed. The statistical analysis was carried out with the Student's t-test. The 24-hour urinary cortisol levels were measured by using commercial RIA Kits (Radim, Pomezia, Italy). In AD, the 24-hour urinary free cortisol was 53.18 ± 17.49 μg/day, significantly higher than that of the C group (37.16 ± 15.95 μg/day) (p <0.001) and similar to that of the VD group (59.04 ± 30.19 μg/day). Although a hyperactivity of HPA axis function is not a specific marker of dementia, our study in two forms of dementia with different etiology, like AD and VD, has revealed a common sign of hyperactivity of the HPA axis function. We conclude that further studies of HPA axis may be helpful for our understanding in the pathogenesis of dementia.