Hi Sammy,
It can also stand for Elderly Mentally Infirm.
Either way, it's a shorthand was of describing services/homes for people with dementia.
For example, when you search for care homes and services on the Commission for Social Care Inspection's web site:
you will see a checkbox for "Dementia(EMI)" which means the home is licensed to provide a set number of places for people with dementia.
Take care,
Sandy
