Controversy About Lack of Placebo Group Decline in Alzheimer's Clini...( - Two Large-Scale Analyses Have C...),Health

- Two Large-Scale Analyses Have Conflicting Results -

CHICAGO, July 28 /PRNewswire-USNewswire/ -- Lack of measureable decline in memory and thinking processes among placebo groups in Alzheimer's disease clinical trials might reduce the ability to show the effectiveness of new Alzheimer therapies, according to new research reported today at the 2008 Alzheimer's Association International Conference on Alzheimer's Disease (ICAD 2008) in Chicago.

Alzheimer clinical trials seek to show that those who received the treatment improved over the course of the study when compared to those who received the placebo, or that they got worse to a lesser degree. A complication that is emerging in Alzheimer clinical trials is the perception that participants with Alzheimer's in the placebo arms of the trials are showing less worsening over the time period of current studies. It has been speculated that this may be due to:

-- Inadequate sensitivity of the standard scales used for measuring cognition in these trials.

-- Differences in disease severity and co-existing medical conditions between the populations being recruited now compared with previous trials.

-- The relatively common use of the currently approved Alzheimer drugs (cholinesterase inhibitors and memantine) by populations involved in the clinical trials.

"In Alzheimer trials, if the placebo group does not worsen over the course of the trial then it might be very difficult, or even impossible, to show that a drug is effective," said William Thies, PhD, vice president for Medical & Scientific Relations at the Alzheimer's Association.

Two scientific presentations from ICAD 2008 address the issue head on -- one through a review of 87 Alzheimer clinical trials conducted between 1991 and 2005, and the second by specifically looking at trials of the drug donepezil from 1990 to 1999.

Analysis of Multiple Studies Reveals Process to Ensure Placebo Group Decline

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