To clarify the characteristic of impaired and unimpaired Instrumental Activities of daily living (IADL) processes with the severity of cognitive impairment in community-dwelling older adults with Alzheimer’s disease (AD) using the Process Analysis of Daily Activity for Dementia (PADA-D).

Cross-sectional study.

13 medical and care centers in Japan.

115 community-dwelling older adults with AD.

The severity of cognitive impairment was classified by Mini-Mental State Examination (20 ≥ mild group, 20 < moderate group ≥ 10, 10 < severe group), and IADL scores and eight IADL items in PADA-D were compared among three groups after adjusting for covariates. Rate of five feasible processes included in each IADL of PADA-D was compared.

IADL score showed a decrease in independence with the severity of AD except for Use modes of transportation and Managing finances, which was especially pronounced in Shopping (F = 25.58), Ability to use the telephone (F = 16.75), and Managing medication (F = 13.1). However, when the PADA-D was examined by process, some processes that were impaired and unimpaired with the severity of cognitive impairment were clear. For example, Plan a meal was impaired (ES = 0.29) with the severity, but Prepare the food was not in Cooking performance.

We suggested that detailed process analysis in IADLs can clarify the characteristic of processes that are impaired and unimpaired with the severity of cognitive impairment in older adults with AD living in the community. Our findings may be useful for rehabilitation and care in IADL to continue living at home.