Utility of the Neurobehavioral Cognitive Status Examination (COGNISTAT) in differentiating between depressive states in late-life depression and late-onset Alzheimer's disease: a preliminary study

Background: It is often difficult to differentiate between the depressive states seen in late-life depression and late-onset Alzheimer' disease (AD) in the clinical setting. Methods: Thirty-four outpatients were recruited, all fulfilling the criteria of aged 65 years or above, scores of 14 or more on the Hamilton depression rating scale (HAM-D), and 26 or less on the Mini-Mental State Examination (MMSE). At the initial visit, they were administered the Neurobehavioral Cognitive Status Examination (COGNISTAT). At 1 month, a diagnosis of either senile depression (n = 24) or Alzheimer' disease (n = 10) was made. Results: The COGNISTAT revealed that the late-life depression group showed significantly higher scores in orientation and comprehension subtests compared with the AD group. At the study endpoint (6 months after treatment), MMSE detected significant improvements in the late-life depression group (n = 15), but no changes in the late-onset AD group (n = 7). Scores for memory, similarities, and judgment on the second COGNISTAT were significantly improved in the depressed group, whereas calculation scores deteriorated significantly in the AD group. Conclusion: The COGNISTAT could prove useful in differentiating late-life depression from late-onset AD, despite similar scores on MMSE.