Factors influencing survival among patients with vascular dementia and Alzheimer's disease

Abstract

Vascular dementia (VAD) and dementia of the Alzheimer type (DAT) are malignant conditions of the elderly. More information is required to clarify expected lengths of survival, which condition is more lethal, and which risk factors may influence survival duration. Cross-sectional and longitudinal designs were used. Survival interval was the period after study admission to death. From a population of 392 patients (of the 150 patients with VAD, mean age at entry was 68.3 years, of the 242 patients with DAT, mean age at entry was 73.0 years), there were 52 deaths, 26 patients with VAD and 26 patients with DAT. Pre-entry dementia symptoms were present for a mean of 3.1 years, with median follow-up of 3.6 years. Among 236 control subjects, there were 19 deaths. Entry age was 69.5 years, with median follow-up of 8.8 years. Influences of risk factors for stroke and body mass index on symptom duration, survival intervals, and cause of death were evaluated. Family history of neurodegenerative disorders, principally DAT, negatively influenced DAT survival. Body mass index declined with age and duration of pre-entry symptoms among men and women in all three groups. Before entry, for men, dementia symptoms were present for shorter periods compared with women. After entry, VAD and DAT patients had similar survival intervals. Causes of death were similarly distributed (78% of patients with VAD died from vascular causes, 56% of patients with DAT and 67% of the controls). VAD and DAT are malignant conditions negatively influencing survival times. Being a woman seems to play a protective role in symptom duration before diagnosis, but after diagnosis survival times of men and women were similar. We attribute equivalence of survival intervals among dementia groups to control of risk factors for cerebrovascular disease.