Delusion of theft and phantom intruder delusion in demented elderly patients in Japan.

Delusion of theft and phantom intruder delusion are among the most frequent delusions in dementia. The purpose of this study was to clarify the clinical characteristics of patients with these symptoms. The authors conducted a questionnaire survey; items included age, gender, dementia diagnosis, cognitive function, and activities of daily living. Other clinical characteristics were evaluated using the quality of life questionnaire for dementia. A total of 217 patients with dementia were rated. Frequencies of delusion of theft were as follows: frequent, 7%; sometimes, 11%; rare, 16%; and none, 66%. Frequencies of phantom intruder delusion were as follows: frequent, 4%; sometimes, 10%; rare, 9%; and none, 77%. Comparison between positive and negative groups with these symptoms revealed that positive groups had higher scores in 2 of 6 domains of the quality of life questionnaire for dementia, namely, negative affect and actions, and restlessness. The positive group with delusion of theft had higher scores in cognitive function and activities of daily living than did the negative group. These results suggest that negative affect and action and restlessness might be related to delusion of theft or phantom intruder delusion and that delusion of theft frequently occurs in the early stage of dementia.