LONDON (Reuters) -- Substances in cerebrospinal fluid could be used to diagnose elderly people with early signs of Alzheimer's disease, scientists said on Monday.

Confusion and loss of memory can either be early indications of dementia that will progress over time or normal signs of aging. Determining which patients will progress to Alzheimer's disease is difficult.

But scientists in Sweden have found that compounds, or biomarkers, in cerebrospinal fluid could be a diagnostic tool to help determine early signs of Alzheimer's.

"Using these biomarkers, we can identify patients with Alzheimer's disease when they have only mild memory disturbances," said Kaj Blennow, of Sahlgrenska University Hospital in Goteborg, Sweden.

"We can detect this very early."

Although there is no cure for Alzheimer's, early diagnosis is important because drugs can improve symptoms of the illness.

An estimated 12 million people worldwide suffer from Alzheimer's disease, the leading cause of dementia in the elderly. The number is expected to increase as the population ages.

Blennow and his colleagues found that elderly people with mild cognitive impairment who have raised levels of b-amyloid, and tau biomarkers in cerebrospinal fluid were more likely to suffer from Alzheimer's.

They extracted the fluid from 137 patients with mild cognitive impairment and 39 healthy volunteers. After a 4-5 year follow-up, 42 percent of patients had developed Alzheimer's disease and 15 percent suffered from other types of dementia.

Patients with abnormal concentrations of biomarkers were more likely to develop Alzheimer's disease, according to the research reported in The Lancet Neurology.

The researchers believe the biomarkers should be combined with clinical examinations and other tools such as brain imaging and cognitive tests to diagnose early Alzheimer's disease.