Dementia patients are being dumped in hospitals in England because of a lack of community care, a charity says.
The Alzheimer's Society called for action, highlighting data showing one in 10 dementia patients spends over a month in hospital after being admitted.
The figures also suggested the overall number of emergency admissions among people with dementia is rising - with some patients yo-yoing back and forth.
Ministers said they were "determined" to tackle the problems.
Central to this, the government said, would be plans for reforming the social care system, which encompasses care home places and support in people's homes.
A Department of Health and Social Care spokeswoman said a long-term solution would be found to ensure dementia patients were treated with "dignity".
"We know that hospital visits can be distressing for people with dementia which is why there should be high-quality care in the community," she added.
'My mum spent most of her last year in hospital'
Dorothy Boschi had to be admitted to hospital three times during her last year of life after having falls and contracting infections.
Each time led to lengthy stays - she spent seven months in hospital in total.
Her daughter, Daphne, 63, from South Gloucestershire, said this continued even when doctors decided she was ready to be discharged because support could not be found to look after her in the community.
She died in January last year, aged 97.
Daphne said the situation led to her mother becoming "angrier, depressed and more frustrated" in her final months.
"Everything was a battle to get proper care. The whole system has lost sight of the person they are meant to be providing care for."
What has the charity found?
The Alzheimer's Society analysed hospital records covering emergency admissions in the six years to 2017-18.
It found 379,000 cases where dementia had been recorded on admission - a rise of 100,000 since 2012-13.
This represents just a small fraction of the six million emergency admissions that year - although that is likely to be an underestimate as the condition is not always recorded on hospital systems.
The charity believes around a quarter of patients in hospital at any one point will have dementia.
Around 40,000 of the dementia admissions - one in 10 - spent longer than 28 days in hospital.
Alzheimer's Society chief executive Jeremy Hughes said people were falling through the "cracks of our broken social care system".
"People with dementia are all too often being dumped in hospital and left there. Many are only admitted because there's no social care support to keep them safe at home.
"They are commonly spending more than twice as long in hospital as needed, confused and scared."