The association between activities of daily living and long hours of care provided by informal caregivers using a nationally representative survey in Japan.

•We determined the relationship between long hours of care and the assistance in each activity of daily living (ADL) element.•The assistance in wiping of the body, dressing and toileting were significantly associated with longer hours of care .•To support caregivers effectively, it is important to consider the kinds of ADL elements of the care recipients.