Dexamethasone Suppression Test in Dementia

To the Editor:-We have previously reported a high rate of dexamethasone nonsuppression in dementia,’ a finding that prompted us to investigate the performance of the dexamethasone suppression test (DST) using the same procedure in a further group of demented patients and examine its relationship to cognitive, behavioral and cortical dysfunction. The DST was carried out in 23 male and 37 female demented patients including 14 patients admitted to a psychogeriatric assessment ward, 29 electively admitted patients into a research ward, and 17 long-term patients in comparison with 37 normal control subjects. They were diagnosed in accordance with the International Classification of Mental Disorders and were rated on the Hachinski scale.2 The group of electively admitted patients received a large battery of clinical and biological investigations including cognitive, behavioral rating scales, and tests of cortical function (object recognition, aphasia, agnosia, right/left disorientation, facelhand tests, apraxia, dyscalculia, logical reasoning, motor sequencing, writing, and reading tests). They also had a computerized tomography (CT) scan. The whole group of demented had a significantly higher rate of DST nonsuppression (65%) in comparison with control subjects (11%) (P < 0.001). There was no association between DST and age or sex in patients or controls. Patients with high Hachinski scores (7 + ) indicating multi-infarct dementia had a higher rate of nonsuppression (72%) than those with low scores (< 4) indicating senile dementia of the Alzheimer’s type (56%). Patients admitted to the acute assessment ward had the highest rate of nonsuppression (86%) compared to the group of elective admissions who had the lowest rate (55%) while the longterm patients had a similar rate to the whole group of patient (65%). There was a trend for patients with abnormal DST to have a lower mean weight than those with normal DST (P < 0.07). There were no associations between DST and cognitive and cortical function tests, with the presence of physical or biochemical abnormalities, or with the degree of abnormality on the CT scan. On the behavioral rating scale, however, those with abnormal DST had a higher percentage of patients observed to be depressed (50%) (visibly distressed in association with sleep and appetite disturbance), than those with normal DST (15%) (P < 0.06). These results confirm our previous findings and those of other investigator^.^ The very high rate of DST nonsuppression (86%) in those admitted to the acute assessment ward may be related to the “stress” of hospitalization as has been recently ~ugges ted .~ The trend for an association between greater DST abnormality and depressive symptoms in dementia is in harmony with the findings of other worker^.^,^ These findings cast further doubt on the diagnostic value of DST in the depression. Its prognostic value in depression and other psychiatric illness however remains to be further in~estigated.~