Background Vascular causes and factors remain the most significant preventable component of cognitive disorders of elderly individuals. The Hachinski Ischemic Score (HIS) is the questionnaire most commonly used for diagnosis of vascular dementia.
Objective To consolidate and further validate the HIS.
Design The Canadian Study for Health and Aging was used for this study. It was a cohort study conducted in 3 waves in 1991, 1996-1997, and 2001-2002. The HIS containing 13 items was subjected to correspondence analysis to identify its optimal scaling of item scores and minimal set of items while maximizing the explainable variance.
Setting A community-based cohort study.
Patients For this analysis, we used 2968 of 3054 well-characterized and well-diagnosed cases with complete HIS data (86 cases had ≥1 item missing) from Canadian Study for Health and Aging phases 2 (1996-1997; n = 2431) and 3 (2001-2002; n = 623).
Results Two optimized HIS versions were identified that classify patients with vascular dementia vs those with nonvascular dementia as well as or more accurately than the original HIS instrument. Assuming the HIS instrument measures only a single dimension, correspondence analysis identified the 7 most discriminative HIS items. Binary scoring (0, 1) of these items led to a 7-item HIS model that classified as well as the original 13-item HIS instrument. By merging highly similar HIS items and applying correspondence analysis, a 5-item composite HIS model was created that measures 2 meaningful dimensions of information and classified vascular vs nonvascular dementia better than the original HIS instrument. Each HIS version developed has specific advantages and disadvantages in terms of simplicity, scoring, generalizability, and accuracy.
Conclusion Depending on the specific setting, 2 reduced HIS versions consisting of 5 composite-question items or 7 single-question items classify as well as or better than the original HIS instrument.