Is ischemic cerebrovascular disease a risk factor for dementia in patients with Parkinson's disease?

Dear Sirs, We read with great interest the study by Haugarvoll et al. reporting on the influence of cerebrovascular risk factors on incident dementia in patients with Parkinson’s disease (PD) (1). After conducting a well designed, prospective study on a large, representative cohort of patients with PD, the authors concluded that cerebrovascular risk factors were not associated with incident dementia, which may be attributed to PD-related degenerative brain changes. Indeed, many studies have associated dementia in PD with the presence of cortical Lewy body (2, 3) and Alzheimer’s disease pathology (4). Several others have failed to relate cerebrovascular risk factors (5, 6) or cerebrovascular neuropathology (7, 8) with dementia in PD. In a recent clinicopathological study on 97 PD brain donors, our group reported no association between ischemic cerebrovascular disease and specific phenotypic characteristics of PD (including dementia) (7). Although cerebrovascular risk factors may not be associated with dementia in PD, they have been linked to increased disease severity in late-onset patients (9). To further explore the possible contribution of ischemic cerebrovascular disease on dementia in PD, we present data from an extended cohort of 150 consecutive brain donors from the University of Miami Brain Endowment with a clinical and pathological diagnosis of PD (banked over a period of 15 years). The methods used for donor recruitment, post-mortem examinations as well as the clinical (for PD and dementia) and pathological diagnostic criteria have been described previously (4, 10). The presence of ischemic cerebrovascular lesions in the cerebral hemispheres, brainstem and cerebellum was documented by inspection of gross brain specimens and by neurohistological evaluation. Comparisons were made between PD patients with neuropathologic evidence of (n 1⁄4 43) ischemic cerebrovascular lesions (PDv) and those without (n 1⁄4 107) (PDnv). Statistical analysis was performed using the SPSS for Windows release 11.0 (SPSS Inc., Chicago, IL, USA). Comparisons of continuous data were carried out using Mann– Whitney U-test for two samples. Categorical data were analyzed using chi-squared test with Yates corrected P-value. P < 0.05 was considered significant. Multiple logistic analysis with ischemic cerebrovascular disease as the dependent variable was performed to adjust for age and disease duration. The study was approved by the local Institutional Review Board. The prevalence of ischemic cerebrovascular disease in our cohort was 28.7% (n 1⁄4 43/150) [subcortical/lacunar n 1⁄4 24, (55.8%), cortical (n 1⁄4 10, 23.3%), combination n 1⁄4 9, (20.9%)]. Similar prevalence rates have been reported in previous clinicopathological studies (8, 11, 12). The characteristics of PDv and PDnv patients and results of the comparisons are summarized in Table 1. There were no statistically significant differences in the prevalence of dementia between groups. None of the variables studied gained statistical significance after the multiple logistic regression analysis. The present study has several limitations – its retrospective nature, the possibility of inconsistent recording of symptoms, and the possible selection bias being the most important.