Background: The validity of Hachinski Ischemic Score (HIS) in differentiating between Alzheimer’s disease (AD) and Vascular dementia(VaD) has been questioned and compared with the gold standard autopsy.

Objective: To confirm that the HIS can be used to differentiate related VaD from AD in a Thai population.

Material and Method: A prospective study of 398 patients who were attending the Memory Clinic, at Siriraj Hospital between January 2001 and October 2003.

Results: The 214 patients, with a mean age of 71.15 ± 10.20 years, were classified as AD, VaD or mixed dementia (AD with cerebrovascular disease) in proportion of 60.2%, 30.4%, and 9.3% respectively. The authors propose HIS at 5 as a cut off point to differentiate patients with AD and those with VaD or AD with cerebrovascular disease with sensitivity of 85.3% and specificity of 72.9%.

Conclusion: The HIS can be applied to differentiate dementia related vascular etiology from AD in a Thai population.

Keywords: Hachinski Ischemic score, Alzheimer disease, Vascular dementia, Mixed dementia, Thai