Jul. 13, 2009 (United Press International) -- Two studies indicate treatments of Alzheimer's are not effective unless the disease is found early, researchers reported in Vienna.

The two studies used DHA, an omega 3 fatty acid. Subjects for the 18-month trial had mild to moderate Alzheimer's.

One trial was by the Alzheimer's Disease Cooperative Study, supported by the National Institute on Aging. The other was by Martek Biosciences Corporation (NASDAQ:MATK) , the firm that makes DHA.

Researchers presented their studies Sunday at the Alzheimer's Association 2009 International Conference on Alzheimer's Disease.

The only positive results on tests of memory and learning came from healthy older adults, not people with Alzheimer's or other dementias. The studies showed results similar to those from other recent Alzheimer's therapy trials.

They "raise the possibility that treatments for Alzheimer's must be given very early in the disease," said William Thies, chief medical and scientific officer at the Alzheimer's Association.