Controversy About Lack of Placebo Group Decline in Alzheimer's Clini...(n S. Schneider MD professor of psychiatr...),Health

Date:7/28/2008

n S. Schneider, MD, professor of psychiatry and neurology at the University of Southern California Keck School of Medicine, and professor of gerontology at the USC Leonard Davis School of Gerontology and colleagues searched published and unpublished sources for six months or longer randomized, double-blind, placebo-controlled Alzheimer clinical trials. They found 103 trials conducted between 1991 and 2005 and obtained information from 87. From these they extracted information about trial size, countries, number of sites, treatment allocation ratios, enrollment dates, age, gender, and scores on two standard measures of cognition -- the Mini-Mental State Examination (MMSE) and the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog).

The researchers found no changes in amounts of cognitive decline across the 15-year time period of the trials. They found that smaller placebo groups were associated with less likelihood of cognitive worsening over the course of the trial. Placebo group sample sizes less than 100 had a 37 percent chance of not showing significant change, while samples greater then 200 all showed significant worsening at six months. In 12-month studies, 95 percent of placebo group sample sizes greater then 100 showed significant decline.

Several other factors were found to be associated with whether or not there was cognitive decline in the placebo group. Studies with non-English speaking trial sites were associated with less cognitive worsening over the course of the clinical trial. Use of more frequent cognitive assessments reduced the amount of variance in the amount of worsening. Use of cholinesterase inhibitors was not associated with less cognitive decline during clinical trials.

"Experts have no need to worry that people with Alzheimer's in clinical trials are less likely to worsen than they have before, or that cholinesterase inhibitors are lessening decline of placebo treated patients in recent trials," Schneider
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SOURCE Alzheimer's Association Copyright©2008 PR Newswire. All rights reserved

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