Just what someone needs who is living with dementia - more brain damage! If a place (home or in care setting) is set up correctly, then the agitation of people living with dementia can be helped by listening to them and seeing the world through their eyes/ears. It takes imagination and insight, but it can be done. People who shout a lot, for instance, can be shouting just to hear their voice. Some people can lose their identity so much, they aren't aware of themselves. That is just one example and there are many other reasons for shouting a lot.
Work by David Sheard is really brilliant in giving insights into how to manage and care for people living with dementia through all the different stages they live through.
ECT? Just plain cruel and vicious. It can't give any furthering of care, just doing this for the sake of those who look after them, not to improve the condition for the person themselves. But then ECT is cruel and inhuman - I speak as one who had it forced on me when I was 24.
Really can't see the sense of using this for dementia. Any non professional who has been involved in caring with dementia knows that there are "tricks" to easing the agitation. Can be a bit difficult to pin point the cause of the agitation but ECT can't be the way to go.