Objective: Despite the considerable importance of maintaining support for instrumental activities of daily living (IADLs) for patients with dementia living at home, there have been no formal investigations of what factors influence IADLs.

Method: We administered various neuropsychological tests, the Timed Up and Go [TUG] test, and the Geriatric Depression Screening Scale-15 to 54 individuals in Japan who had visited a day care center or a preventative care class and who had either 23 mild Alzheimer's disease (mild AD) or 31 no dementia. IADLs were measured using the Self-Report Frenchay Activities Index.

Results: The factors related to the domestic chores subscale of the Frenchay Activities Index were gender, backward digit recall performance (Wechsler Memory Scale-Revised [WMS-R]), and TUG test performance ( R ² = 0.53). Factors related to the leisure/work subscale were backward digit recall and logical memory II performance on the WMS-R, scores on the Behavioral Assessment of the Dysexecutive Syndrome, and TUG test performance ( R ² = 0.66). Finally, factors related to the outdoor subscale were backward digit recall, logical memory II, and the TUG test performance ( R ² = 0.62).

Conclusions: The factors affecting IADLs among elderly individuals with mild AD or no dementia vary depending on the type of IADL. Notably, TUG test performance has a direct influence on all IADL types, and might relate to cognitive function. When providing preventative care or IADL support, it may be beneficial to evaluate and intervene with a focus on the cognitive and physical functions highlighted in this study.