Reliability and validity of the Japanese version of the Dysexecutive Questionnaire (DEX) in Alzheimer's disease: validation of a behavioral rating scale to assess dysexecutive symptoms in Japanese patients with Alzheimer's disease.

BACKGROUND: Both executive cognitive dysfunction and behavioral problems contribute to dysexecutive symptoms in daily life. The aim of the present study was to develop a behavior rating scale for assessing dysexecutive symptoms in Japanese patients with AD.

METHOD: The Dysexecutive Questionnaire (DEX), devised by Burgess et al. (1998), was used to evaluate 122 Japanese patients with AD. The factor structure, internal consistency, test-retest reliability, and construct validity of the Japanese version of the DEX were then examined.

RESULTS: The Japanese version of the DEX demonstrated a good internal reliability and a good test-retest reliability. Factor analysis revealed three factors that were named 'apathy', 'hyperactivity' and 'planning and monitoring process of the purposive action'. The 'apathy' factor of the DEX was significantly correlated with the 'apathy' score of the Neuropsychiatric Inventory (NPI), while 'planning and monitoring process' factor of the DEX was significantly correlated with the total score of the Frontal Assessment Battery (FAB) and the 'hyperactivity' factor of the DEX was significantly correlated with the 'aggression', 'euphoria' and 'disinhibition' scores of the NPI.

CONCLUSIONS: The Japanese DEX is a reliable and valid instrument for assessing executive dysfunction conveniently in real life situations of AD patients. While two factors, 'apathy' and 'hyperactivity', were associated with emotional and behavioral changes, the 'planning and monitoring process' was associated with the cognitive executive function in the patients with AD. These findings suggest that both a neuropsychiatric syndrome and cognitive function contribute to the dysexecutive symptoms experienced by AD patients in daily life.