The paper reviewed here is ‘Differentiating the Cognitive Profile of Schizophrenia from that of Alzheimer Disease and Depression in Later Life’ by Mulsant and colleagues and freely available here. In the abstract the authors conclude that
‘Patients with LLS (Late Life Schizophrenia) have a different cognitive profile than patients with AD (Alzheimer’s Disease) or DEP (Depression in later life). Particularly, memory impairment in LLS seems to be more pronounced in learning than recall‘
- All cases referred to a memory service for consultation were analysed. I wasn’t absolutely clear if this was done retrospectively or prospectively but from the wording it seemed to be retrospective.
- People referred to the service underwent psychiatric and neurological assessments and DSM-IV criteria were used for the diagnoses
- All people referred to the service underwent the following neuropsychological test battery as routine and these test scores were included in the analysis
- Animal Fluency
- Boston Naming Test
- Clock Drawing Test – Freedman Scale
- California Verbal Learning Test II – Short Form (CVLT)
- Dementia Rating Scale-2 (DRS)
- FAS Letter Fluency (FAS)
- Luria Alternating Diagrams
- Mini-Mental Status Examination
- Trail Making Test A and B
- Wisconsin Card Sorting Test – 64
- It didn’t look as though a single specific hypothesis was being tested. Instead the demographics and cognitive test results from the different groups – DEP, AD, LLS and control group were being compared.
- In the first phase of the statistical analysis, ANOVA was used.
- When differences between groups were identified using the ANOVA, a Bonferroni correction was made for multiple comparisons
- Cohen’s D was used for differences between the LLS and other groups
- LLS (n=25)
- AD (n=15)
- DEP (n=15)
- NC (n=12)
- I thought Figure 1 was a very useful summary of the data and quite intuitive. The Late onset Schizophrenia group are acting as the reference group. In this diagram, group differences at p<0.001 are highlighted with ***. From looking at differences of this significance I noted the following
- The LLS group were significantly better on a number of memory tasks than the AD group
- The control and DEP groups were significantly better than the LLS group on the FAS, DRM memory, WCST categories, CVLT short and long delay free recall
- I wondered if the latter findings were tapping predominantly into frontal lobe function and the AD group findings into medial temporal lobe function
- In the discussion, the authors comment on the hierarchy of memory impairment across groups
- The researchers note that the groups have small sample sizes which would reduce the power of the study
- They note the memory impairment of the LLS group compared to the DES and control groups on a number of memory tasks
I thought this was a neat study, showing how service data can be effectively utilised to examine group differences in cognition. This research approach should be reproducible across other services although the components of the test battery will vary. Even so, examination of group differences including vascular dementia and frontotemporal dementia using different test batteries would be valuable.
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