Jan. 2, 2010 – The idea that a simple herbal
supplement – Ginkgo biloba - could slow the rate of cognitive decline
has long attracted the attention of senior citizens. The final blow to
that possibility seems to have been struck by a study reported in the
December 23/30 issue of the Journal of the American Medical Association
(JAMA).
"Ginkgo biloba is marketed widely and used with the
hope of improving, preventing, or delaying cognitive impairment
associated with aging and neurodegenerative disorders such as Alzheimer
disease," the authors write.
"Indeed, in the United States and particularly in
Europe, G biloba is perhaps the most widely used herbal treatment
consumed specifically to prevent age-related cognitive decline."
However, evidence from large clinical trials regarding its effect on
long-term cognitive functioning has been lacking.
Beth E. Snitz, Ph.D., of the University of
Pittsburgh, and colleagues analyzed outcomes from the Ginkgo Evaluation
of Memory (GEM) study to determine if G biloba slowed the rate of
cognitive decline in older adults who had normal cognition or mild
cognitive impairment (MCI) at the beginning of the study.
The GEM study previously found that G biloba was
not effective in reducing the incidence of Alzheimer dementia or
dementia overall.
This randomized, double-blind, placebo-controlled
clinical trial included 3,069 community-dwelling participants, ages 72
to 96 years, who received a twice-daily dose of 120-mg extract of G
biloba (n = 1,545) or identical-appearing placebo (n = 1,524).
The study was conducted at six academic medical
centers in the United States between 2000 and 2008, with a median
(midpoint) follow-up of 6.1 years. Change in cognition was assessed by
various tests and measures.
In this study, the largest randomized controlled
trial of G biloba to report on outcomes to date, the researchers found
no evidence for an effect of G biloba on global cognitive change and no
evidence of effect on specific cognitive domains of memory, language,
attention, visuospatial abilities and executive functions.
They also found no evidence for differences in
treatment effects by age, sex, race, education or baseline cognitive
status (MCI vs. normal cognition).
"In sum, we find no evidence that G biloba slows
the rate of cognitive decline in older adults. These findings are
consistent with previous smaller studies examining prevention of decline
and facilitation of cognitive performance and with the 2009 Cochrane
review of G biloba for dementia and cognitive impairment."
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