Risk factors for delusion of theft in patients with Alzheimer's disease showing mild dementia in Japan.

The mechanism underlying delusion in Alzheimer's disease patients has not been fully clarified; however, the occurrence of delusion is a critical issue for dementia patients and their caregivers. In Japan, delusion of theft is the most frequent delusion in AD patients. We examined the risk factors for delusion of theft in AD patients showing mild dementia. Fifty-six AD patients were administered HDS-R, MMSE and COGNISTAT, including the 'speech sample', to assess their neuropsychological and social cognitive functions. The age, years of education, presence of cohabiting family members and premorbid personality traits were obtained from family members. About 25.0% of AD patients showed delusion of theft (D-group), and 75% did not (non-D-group). About 33.3% of female patients and 5.9% of male patients were included in the D-group (p < 0.05). About 13.6% of patients who were cohabiting with family members and 66.7% of patients who were living alone were included in the D-group (p < 0.05). About 35.1% of patients who had a neurotic personality and 5.3% of patients who did not were included in the D-group (p < 0.05). There were no significant differences in scores on HDS-R, MMSE and COGNISTAT sub-scales, except for 'speech sample', between the two groups. In the 'speech sample', 38.7% of patients who understood a relationship between two boys and 12.0% of patients who did not were included in the D-group (p < 0.05). These results indicated that delusion of theft in AD patients was related to female gender, absence of cohabiting family members, neurotic personality and retained social cognitive function.