Latest figures reveal there are almost 5,500 living in central Lancashire who have dementia.
However, it is believed that around half the people who have dementia have not been diagnosed and are living with the disease without receiving the help and support they need.
The Alzheimer’s Society has revealed an increase in the number of people living with dementia with 42,000 people diagnosed with the condition - an increase of almost 4,000 since last year.
However, there are thought to be another 43,000 people living with the condition who have not been diagnosed yet.
In the central Lancashire area which includes Preston and surrounding areas, there were 2,544 diagnosed with dementia in 2012 compared to 2,313 in 2011.
However, the total number of people with dementia in central Lancashire including those who have not yet been diagnosed is 5,491.
Stephen Hughes, support services manager for Lancashire for the Alzheimer’s Society, said: “It is a good thing that the number of people diagnosed with dementia has increased as this means that people are getting access to the help and support they need.
“But at the moment, only around half of the people who have dementia have been diagnosed and we want to ensure that everyone who has dementia gets diagnosed.
“When people are undiagnosed, they can be scared and worried and they are not getting the support they need.
“There are drugs that can alleviate the symptoms of dementia and slow down the onset of the disease, but there needs to be a diagnosis.”
Helen Foster, area manager for the Alzheimer’s Society in the North West, said: “The NHS has made a commitment to improving diagnosis rates so now it is time for that commitment to turn into action locally.”