DELIRIUM AND THE DEXAMETHASONE SUPPRESSION TEST IN THE ELDERLY

It has been suggested that delirium in the elderly is caused by abnorm ally high levels of circulating glucocorticoids or by an increased vul nerability to their effects. We performed a dexamethasone suppression test (DST) in 16 consecutive patients without depression or dementia a dmitted to an acute-care geriatric unit with a clinical diagnosis of l ower respiratory tract infection. Seven of 9 (78%) patients who develo ped delirium were non-suppressors on the DST compared with 1 of 7 (14% ) patients without delirium (p = 0.04). Clinical and laboratory indica tors of the severity of illness did not differ between the two groups. Of the 8 patients with an abnormal DST, 1 died and another was not av ailable for repeat assessment. On re-examination 8 weeks later, after resolution of the delirium and of the chest infection, 5 of 6 non-supp ressors still had an abnormal DST. It is known that some non-demented and non-depressed elderly patients fail to suppress cortisol in respon se to 1 mg of dexamethasone. Our results suggest that such patients ma y be at increased risk for developing delirium during acute illness.