Impact of vascular pathology on survival times of 173 dementia patients -: Hachinski's ischemic score as a predictive tool for clinical purposes

Alzheimer's disease and vascular dementia still may be looked upon as distinct nosologic entities, representing the two main etiologic categories of senile dementia. However, rather recent findings suggest a comorbidity of neurodegenerative and ischemic pathology in a majority of dementia cases in later life. The effect of the vascular pathology on the survival time was studied in 173 dementia outpatients. For 147 patients with complete datasets, we were able to gain information concerning their survival time. As an indicator of cerebrovascular morbidity the 18-point ischemic scale of Hachinski (HIS) was correlated with the survival time. Thus, we did not use the HIS for its original purpose to differentiate between degenerative and vascular dementia, but to roughly evaluate the cerebrovascular impact in a continuum model. Using the Cox model we calculated mortality risks for every point on the HIS. We found a Cox hazard ratio of 1.038 for each supplementary point on the HIS, which equals a 3.8% higher relative mortality risk. The result misses significance (p = 0.092), but indicates a clear tendency towards a shortening of survival time by vascular comorbidity. Future prospective studies should integrate brain imaging to further corroborate our findings.