About 700,000 in the UK have dementia
Anti-psychotic drugs are needlessly being used on many dementia patients.
In some cases, it is even contributing to their deaths.
But a government-commissioned review has now called for a radically different approach to treatment.
What is the scale of the problem?
Dementia affects 700,000 people in the UK.
About 180,000 of these each year will be given anti-psychotic drugs to manage aggressive behaviour.
But, astonishingly, the expert review suggested they only benefit 36,000 - that is one in five.
What is more, their use is linked to 1,800 deaths, while hundreds more people are left coping with the consequences of stroke and falls.
The Alzheimer's Society says it has been inundated by calls from members who are concerned about how their loved ones are being treated.
How has the situation arisen?
Anti-psychotic drugs were originally used for schizophrenia patients.
But as the numbers with dementia has risen - nearly nine in 10 care home residents have the condition compared to about a fifth 30 years ago - doctors have begun resorting to the drugs to calm agitated and aggressive patients.
The trend, which was totally unplanned, is a reflection of the strain the ageing population is placing on health and social care services.
Most professionals do not get specific training in dementia care and therefore do not know how to prevent aggressive and agitated behaviour developing.
For example, in many cases aggression may be linked to easily solved issues such as hunger, pain or boredom.
What will happen now?
The Department of Health has accepted all of the review's recommendations.
The NHS now has three years to reduce its reliance on these drugs by two thirds.
This will require care homes, hospitals and community staff improving access to therapies such as counselling.
But it will also need - and this is likely to be much more difficult - a culture change in the way care is provided.
Extra training will be offered to help staff caring for dementia patients to understand their needs better.
But campaigners do remain concerned about the lack of funding.
The NHS budget is increasing, but no extra funds are being provided on top of this.
Dementia care already costs £17bn a year - and this bill is likely to spiral in the coming years as the number of people with the condition rises.
What should people do if they are worried about a family member's treatment?
Don't panic. Experts say that for some patients anti-psychotic drugs are still necessary.
The first thing to do is to check whether the patient is being given anti-psychotic drug - the treatment could be another drug specially-designed for treating the condition.
If they are be given an anti-psychotic - and if you are concerned about this - the Alzheimer's Society recommends talking to the GP.
Any use of the drugs should only be a short-term measure and doses should be reduced in time.