A simple test of copying ability and sex define survival in patients with early Alzheimer's disease

Background. We studied whether heterogeneous profiles of cognitive function are relevant to survival in patients with early Alzheimer's disease. Methods. CAMCOG subscales of cognitive function were used as predictors of survival, together with gender in 157 consecutively referred patients with early Alzheimer's disease. Statistical analysis was performed with Cox proportional hazards analysis and Kaplan-Meier survival curves. Survival rates were compared with those in the general population. Results. Eighty patients (51 %) died during the follow-up that extended to 5.7 years, with a median survival of 4.4 years after entry. Only the praxis subscore was statistically significant related to survival (P < 0.0001). Its predictive power was based on only two items, including copying ability for a spiral and a three-dimensional house, independent of age, sex, education, overall CAMCOG score, dementia severity and symptom duration. Kaplan-Meier curves for the combined score of these items (0, 1, or 2) showed three groups with significantly different survival rates for both men and women. Comparison of gender specific survival rates with data from the general population showed that excess mortality was statistically significant (P < 0.01) higher in men (51%) than in women (21%) after follow-up extending to 5 years. Conclusions. A simple test of copying ability defines subgroups of AD patients with large differences in survival rates. This suggests that parietal lobe impairment is an important predictor of mortality in AD. Also, the course of AD may be more benign in women than in men.