A campaign to encourage older people with potential memory loss to seek early advice has led to more seeing their doctor.
But those who did go for help were generally not referred to memory specialists, the study found. Researchers suggest some GPs may be reluctant to hand out a devastating dementia diagnosis, while others may simply have missed the signs.
The initiative, which encouraged 14,500 people with memory problems to attend their GP, had no effect on earlier overall diagnosis of the condition.
But the failure to refer patients meant they missed early treatment.
They were also unable to plan ahead with their families, access drugs, arrange care or plan being taken into a home.
Professor Gill Livingston of University College London led the study, published in a PLOS Medicine Special Issue on Dementia.
She said: “I think one of the problems with GPs is that, as dementia can’t be cured, there is a feeling nothing can be done. But diabetes can’t be cured, yet we don’t stop treating it.
“Others think patients don’t want to be told they have dementia. But an early diagnosis has so many benefits.”
Giving an example, she added: “A family member can be given power of attorney by the patient to handle their financial affairs – patients are very vulnerable when going to the bank.”
Dr Matthew Norton of Alzheimer’s Research UK said: “These results suggest that to increase timely diagnosis, both GPs and patients may need targeting with information about dementia and the importance of a diagnosis.”
Some 850,000 people in Britain have dementia.
This is forecast to reach one million by 2025 and two million by 2050. It is now the country’s biggest killer.