Dementia patients are being left without access to helpful treatments because GPs are failing to spot the condition early enough, experts have warned.
People who are actively screened for the disease live longer than patients who are diagnosed with dementia by their family doctor, according to research studies.
Data from more than 350 UK GP surgeries between 1990 and 2007 was analysed by scientists from the Medical Research Council (MRC).
Life expectancy after dementia as recorded by GPs is analysed in the study, the first of its kind to do so.
Experts found that patients aged 60 to 69 have an average life expectancy of 6.7 years once diagnosed with dementia by their doctors.
The study also found GPs were recording dementia in a non-specific way and were not differentiating between Alzheimer's disease and vascular dementia.
This could affect the types of treatments people receive in the long-term and how their disease is managed.
The research was based on records from more than 135,000 people aged 60 and over.
Dr Greta Rait, who led the study, published online in the British Medical Journal (BMJ), said: "Our findings will help clinicians to make more realistic estimates of life expectancy for patients when they are diagnosed and also assist policymakers in planning services."