Homelessness and cognitive impairment: An exploratory study in Tokyo, Japan

Objective: Homelessness has frequently been associated with neuropsychological impairment. This has been observed using general screening tests for dementia as well as tests of more focal abilities, particularly executive function. Most studies have been of homeless individuals from North America with none reported from Japan. Methods: In this exploratory study we interviewed a sample of 16 homeless adults from Tokyo, Japan, and performed tests of cognitive function, assessed head injury, addictive behaviours (drug use, gambling, alcohol abuse), and recorded details of homelessness history. The cognitive examination involved the Japanese Adult Reading Test to estimate premorbid intelligence quotient, the Wisconsin Card Sorting Test to measure frontal lobe-related cognitive function, and the Mini-Mental State Examination to measure global cognitive impairment associated with dementia. Results: Among the 16 homeless individuals, 7 (44%) displayed global cognitive impairment. In addition, executive function tended to be poor. In contrast, estimated premorbid intelligence quotient was within the normal range. Substance abuse in general was not at a level to cause clinical concern, although a high level of pathological gambling was observed. There were no associations between cognitive function and clinical and addictive behaviour variables, although associations were noted between cognitive scores and time spent homeless. Conclusion: The results suggest high levels of neuropsychological impairment in this sample of homeless adults in Japan. Furthermore, cognitive impairment is acquired rather than developmental in origin, and is proportional to the length of time spent homeless.