Preclinical vascular cognitive impairment and Alzheimer disease: neuropsychological test performance 5 years before diagnosis.

BACKGROUND AND PURPOSE Neuropsychological changes that precede a diagnosis of vascular cognitive impairment (VCI) and the differences between preclinical VCI and Alzheimer disease (AD) are not well understood. We compared the neuropsychological performances of people with incident VCI, incident AD, and no cognitive impairment (NCI) 5 years before their clinical diagnoses. METHODS The Canadian Study of Health and Aging is a prospective, cohort study of 10,263 randomly selected persons age 65 years or older. We studied 332 individuals who had completed a battery of neuropsychological tests and were diagnosed with NCI at baseline. After 5 years, 41 were diagnosed with VCI, 25 with AD, and 266 with NCI. RESULTS At baseline, the incident-VCI group performed worse on a wide range of neuropsychological tests compared with the NCI group. A test of abstract reasoning was selectively low in the incident-VCI group, relative to both the incident-AD and NCI groups. The incident-AD group performed worse at baseline on memory tests compared with incident-VCI and NCI groups. CONCLUSIONS This study suggests a preclinical phase may exist in VCI that differs from that in AD. Neuropsychological measures may aid the design of preventive strategies for VCI.