Ginkgo and Alzheimer's, Forget About It?

Ginkgo biloba in autumn
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Results of a large study conducted in France appear to dash the hopes that use of Ginkgo biloba, long viewed as an herb that aids memory loss, can help prevent Alzheimer's disease. Yet does this mean people should just forget about using Ginkgo for any benefits it may offer individuals at risk for or already experiencing memory loss and a decline in cognitive functioning?

Ginkgo tries its hand at Alzheimer's prevention

The growing threat and presence of Alzheimer's disease among an ever increasing older population, along with the fact that the neurodegenerative condition is so devastating, fuels the urgency behind the desire to discover an effective preventive or cure. Ginkgo biloba has been one of many players in such research, as it has antioxidant and anti-inflammatory properties.

Results of the latest attempt, known as the GuidAge Trial, have been published in Lancet Neurology and come from a French team headed by Bruno Vellas, MD, of Hopital Casselardit in Toulouse. These investigators conducted a randomized, controlled trial that was completed by 2,487 individuals age 70 and older who reported memory problems but were dementia-free when they entered the study.

Study participants were given either 120 mg of Ginkgo biloba extract or a placebo to take twice daily, and they were followed for a median of 5 years. During that time period the following observations were made:

  • Probable Alzheimer's disease developed in 61 people who took Ginkgo (incidence of 1.2 per 100 person-years) and in 73 who took placebo (1.4 per 100 person-years)
  • For diagnoses of mixed dementia or pure Alzheimer's disease, there were 70 among those who took Ginkgo (1.4 per 100 person-years) and 84 among those who took placebo (1.6 per 100 person-years)
  • Incidence of adverse events, including stroke, other hemorrhagic or cardiovascular events, and death were similar for both groups as well
  • Study participants tended to be more educated than the general elderly population

Results of the GuidAge trial support those of some previous research, including the Ginkgo Evaluation of Memory (GEM) trial. That trial included individuals age 75 or older who had no dementia or who had mild cognitive impairment when they entered the study.

Participants were given either 120 mg of Ginkgo biloba taken twice daily (1,545 subjects) or placebo (1,524), and follow-up was for a median of 6.1 years. Dementia developed in 277 people who took ginkgo and 246 who took placebo, demonstrating that "G. biloba at 120 mg twice a day was not effective in reducing either the overall incidence rate of dementia or AD incidence in elderly individuals with normal cognition or those with MCI."

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Ginkgo biloba may still benefit memory
Although ginkgo may not prevent Alzheimer's disease, that is not to say it cannot provide some benefit when it comes to cognition or memory loss. In fact, a number of studies suggest Ginkgo may improve memory and cognitive function. For example:

A recently reported study involved 120 individuals aged 60 to 85 years who had mild cognitive impairment. The participants were randomly assigned to take either 19.2 mg of Ginkgo biloba three times daily or placebo for six months, and they were tested both before and after treatment.

Subjects in the Ginkgo group scored significantly better on logical memory testing and nonsense picture recognition than did those in the placebo group. The researchers concluded that "Ginkgo biloba leaf tablet showed good efficacy in promoting episodic memory function in MCI patients."

In a meta-analysis, nine trials lasting 12 to 52 weeks and that included a total of 2,372 patients were evaluated. Changes in cognition were in favor of Ginkgo when compared with placebo, although the difference was not significant for activities in daily living. The reviewers concluded that "Ginkgo biloba appears more effective than placebo."

Ginkgo biloba: forget about it?
According to Lon Schneider, MD, of the University of Southern California in Los Angeles, commenting in an editorial that accompanied the Lancet Neurology study, "It would be unfortunate if users of ginkgo biloba, nevertheless, are led to believe that the extract prevents the dementia."

He goes on to note that some people "will rationalize that, in the absence of effective treatments, ginkgo biloba could still possibly help, and appearing safe, will not harm them." Given the lack of anything else from the medical community that offers much hope for dealing with memory loss and Alzheimer's, some people are likely not prepared to forget about Ginkgo biloba.

SOURCES:
DeKosky ST et al. Ginkgo biloba for prevention of dementia: a randomized controlled trial. JAMA 2008 Nov 19; 300(19): 2253-62
Schneider LS. Ginkgo and AD: key negatives and lessons from GuidAge. Lancet Neurology 2012; doi:10.1016/S1474-4422(12)70212-0
Vellas B et al. Long-term use of standardized ginkgo biloba extract for the prevention of Alzheimer's disease (GuidAge): a randomized placebo-controlled trial. Lancet Neurology 2012; doi:10.1016/S1474-4422(12)70206-5
Weinmann S et al. Effects of Ginkgo biloba in dementia: systematic review and meta-analysis. BMC Geriatrics 2010 Mar 17; 10:14
Zhao MX et al. Effects of Ginkgo biloba extract in improving episodic memory of patients with mild cognitive impairment: a randomized controlled trial. Zhong Xi Yi Jie He Xue Bao 2012 Jun; 10(6): 628-34can benefit

Image: Morguefile

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