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- Ginkgo (Ginkgo biloba)
- Alzheimer's Disease
- Dementia
| Date:
07-29-2011 | HC#
031153-429
|
Re: High-dose Ginkgo Extract Shows Evidence of Benefit in Alzheimer's Disease
Janssen
IM, Sturtz S, Skipka G, Zentner A, Garrido MV, Busse R. Ginkgo biloba in Alzheimer's disease: a systematic review. Wien Med Wochenschr. 2010;160(21-22):539-546.
Alzheimer's disease
(AD) is the most common form of dementia, accounting for 50-70%. There is no
cure, and symptoms get progressively worse. Symptom management is the goal of
current therapies. The purpose of this systematic review was to evaluate the
beneficial and harmful effects of long-term ginkgo (Ginkgo biloba) leaf extract treatment in patients with AD. The
review was commissioned by the German Institute for Quality and Efficiency in
Health Care.
The following
databases were searched: MEDLINE (1966 to January 2010), EMBASE (1980 to January
2010), The Cochrane Library (Clinical Trials, January 2010), CHID via ADEAR
(October 2005), The Cochrane Database of Systematic Reviews (Cochrane Reviews),
the Database of Abstracts of Reviews of Effects (Other Reviews), and the Health
Technology Assessment Database (Technology Assessments). Clinical trial
registries and study result databases available on the Internet were screened,
as were the websites of the European Medicines Agency (EMA) and the US Food and
Drug Administration (FDA). The search strategy included the terms dementia
(especially AD) and ginkgo (including trade names). Unpublished data on EGb 761
(ginkgo standardized extract) was provided by Dr. Willmar Schwabe GmbH &
Co. KG, Karlsruhe, Germany. The review included randomized, controlled studies with
a follow-up of ≥ 16 weeks. The included studies had to evaluate at least 1
patient-relevant outcome measure (i.e., how patient feels or functions), and
the patients had to have a diagnosis confirmed by standard diagnostic testing
methods.
Six studies were
located that fit all of the criteria. All were double-blind, parallel, multicenter,
randomized controlled trials comparing EGb 761 with placebo. Three of the
studies used only 240 mg/day ginkgo, and two used only 120 mg/day ginkgo, and
one used both ginkgo doses in different subgroups. Treatment duration ranged
from 22 to 26 weeks, with one study treating patients for 52 weeks but
providing an interim 26-week analysis that was utilized for comparability. The
methodological quality of all studies was rated good to excellent. Cognition
was the primary endpoint for all studies, and all studies assessed Activities
of Daily Living (ADL). Despite these similarities, statistical testing
indicates that the studies were highly heterogeneous; having differences in
quality, duration of treatment, dose, inclusion/exclusion criteria, etc. This
prevented the data from being pooled. Overall, methodological quality was good.
When considering the
4 high-dose studies, ginkgo was favored for the ADL and cognition outcomes. Three
studies evaluated general symptoms, and the two with high doses of ginkgo had a
positive effect. Two studies evaluated quality of life; one using 120 mg/day showed
no significant benefit with ginkgo whereas the other 240 mg/day study showed a
benefit. When evaluating safety, there was no evidence of a harmful effect
associated with ginkgo; however, the ginkgo group had significantly more
withdrawals due to adverse events (AEs) compared with placebo. Age and psychopathological
symptoms modified outcomes, but the data were insufficient to adequately
interpret.
The authors conclude
that the high dose of ginkgo can be beneficial in AD; however, the conclusion
is based on very heterogeneous results. Therefore, no potential effect size could
be estimated. Based on the inclusion criteria of the four high-dose studies,
the benefit may only occur in patients with accompanying psychopathological
symptoms. One problem was the substantial heterogeneity between studies that
could not be attributed to a specific factor. The authors conclude that the
results on AEs are inconsistent—there were no serious AEs; however, more ginkgo-treated
patients discontinued the studies due to AEs.
Other reviews have
different conclusions. The authors point out that those other reviews, for
example The Cochrane Review, had different inclusion and exclusion criteria, so the
reviews cannot be compared. The authors state that, "Although this
assessment found beneficial effects of ginkgo for AD
patients, a clear recommendation for the use of ginkgo
cannot be given" because effect size could not be calculated. Long-term
studies comparing ginkgo with other anti-dementia drugs are needed, as are
studies of subgroups of patients with AD.
—Heather S. Oliff, PhD
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