The purpose of this study was to determine relative contributions of first-degree familial and individual risk factors to clinical manifestations of two major age-related dementias. The authors interviewed 183 patients with dementia of the Alzheimer's type (DAT) and 137 patients with ischemic vascular dementia (IVD) together with family members and caregivers. Information was also obtained from medical records and collateral sources as required. Risk factor data within a predictive model for differentiating the two dementias were evaluated. There was a greater incidence of family history of degenerative and dementing neurologic disorders in DAT than in IVD. Both groups were equivalent for family histories of cerebrovascular disease. Despite familial equivalence, patients with IVD had a greater individual incidence of risk factors for cerebrovascular disease. Analysis by gender revealed three observations. Among DAT patients, family history for degenerative and dementing neurologic disorders proved to be significantly greater among women than among men. This risk factor did not, however, predict individual diagnoses for DAT. Women with IVD were more likely to have a family history of cancer than men. Multiple regression analyses revealed that reduced educational levels in women predicted greater liability for IVD than for DAT. Hypertension, heart disease, and diabetes mellitus were all risk factors for IVD, but not for DAT.
Conclusions: Individual and familial historical data provide useful information concerning identification, pathogenesis, prevention, and treatments for vascular dementia but little predictive information for identifying patients with Alzheimer's disease.