Cerebral emboli and depressive symptoms in dementia
Purandare N, Voshaar RC, Hardicre J, Byrne J, McCollum C, Burns A;
Commented by , 26 Oct 2006
Background
Using sophisticated scanning technology, this research group in Manchester, England, have recently published convincing data to suggest increased frequency of spontaneous cerebral emboli in dementia. They have now re-analysed their data to test an association between cerebral emboli and depression in dementia.
Aim
To evaluate the association between spontaneous cerebral emboli and depressive symptoms in Alzheimer’s Disease (AD) and vascular dementia (VaD).
Method
Patients were drawn from a previous study, and had been recruited from secondary care old age psychiatry services: diagnoses of AD and VaD were made by an experienced old age psychiatrist independent of the research team, using strict diagnostic criteria. Patients with severe dementia, and those on anticoagulants, were excluded.
Depressive symtoms were assessed by interview with carers using the Neuropsychiatric Inventory (NPI), which rates depressive symptoms in dementia over the previous month.
Cerebral emboli were measured at a Vascular Studies Unit by technologists blind to diagnoses. Continuous transcranial Doppler insonation of the middle cerebral arteries was recorded for one hour, emboli were identified using international consensus criteria. Blood pressure, carotid ultrasound, lipid profile and a polyprotein E genotype were also recorded.
Statistics Chi-squared was used to determine the univariate relationship between NPI depression scores and the presence of spontaneous cerebral emboli. Multiple logistic regression was then used to analyse confounding variables.
Results
Of the original cohort of 170 patients with dementia, 28 did not have NPI data. Of 142 patients included, 72 had AD, 70 VaD. Mean MMSE score was 21.5. Both groups were similar with respect to age, gender and MMSE score.
Spontaneous cerebral emboli were detected in 40% of patients with both AD and VaD. 13% of the 72 patients with AD and 9% of 70 patients with VaD scored > 4 on the depressive subscale of the NPI: the presence of clinically relevant depressive symptoms was significantly higher in patients with emboli.
Multivariate analysis confirmed the association between emboli and depressive symptoms, but found no other statistical link between cardiovascular risk factors and dementia type, age, gender, or severity of dementia.
Dr Seymour's comments
Recently published research by this study group in the British Medical Journal, showing a very high occurrence of spontaneous cerebral emboli in subjects with both common causes of dementia, is an important contribution in delineating the pathogenesis of dementia.
The authors have now analysed their data further to propose a particular link between depression and cerebral emboli in both vascular dementia and Alzheimer’s Disease. Although direction of causality cannot be assumed, they hypothesize that vascular damage to fronto-striatal pathways by cerebral emboli leads to depression in dementia patients.
The study has a number of limitations. It was a secondary care sample (not representative of the general population); the assessment of depression was limited; and actual numbers of patients with both depression and dementia were small. However, this paper is an important contribution to the literature in hypothesizing that asymptomatic micro emboli might be causally associated with depression in dementia. The authors propose to further avenues of research:
-
longitudinal studies using standardized diagnostic criteria for depression
-
studies with a control group of non-demented late-onset depressives.