Ginkgo biloba fails to prevent Alzheimer’s disease

Researchers in France participating in the GuidAge Study Group assessed the long-term use of standardized ginkgo biloba extract in elderly adults with memory complaints.

First, the details.

• Adults at least 70 years of age who reported memory complaints to their primary-care doctor were randomly assigned to a treatment group.
  • Twice per day dose of 120 mg standardized ginkgo biloba extract (EGb761)
  • Placebo
• Participants were followed for 5 years by primary-care doctors and in expert memory centers.
• The primary outcome was conversion to probable Alzheimer’s disease in participants who received at least one dose of study drug or placebo.
  • The criteria for probable Alzheimer’s disease includes progressive memory loss over more than 6 months, plus at least 1 of the following: atrophy in a particular part of the brain shown by MRI, abnormal biomarker proteins in the cerebrospinal fluid, a specific pattern on PET of the brain, and a genetic mutation for Alzheimer’s disease within the immediate family.
• Neither the patients nor researchers knew the treatment given — double blind.

And, the results by 5 years.

• Alzheimer’s diagnosis
  • 61 participants in the ginkgo group were diagnosed with probable Alzheimer’s disease (1.2 cases per 100 person-years).
  • 73 in the placebo group (1.4 cases per 100 person-years) — not a significant difference.
• Incidence of adverse events did not differ between groups.
• 65 participants in the ginkgo group experienced a stroke vs 60 with placebo — not a significant difference.
• Incidence of other hemorrhagic or cardiovascular events did not differ between groups.

The bottom line?

The authors concluded, “Long-term use of standardized ginkgo biloba extract in this trial did not reduce the risk of progression to Alzheimer’s disease compared with placebo.”

An earlier review of studies with ginkgo to prevent Alzheimer’s disease reported inconsistent results. Although in 1 study, ginkgo and donepezil (Aricept) appeared equally effective over 24 weeks in mild-to-moderate dementia.

The Ginkgo Evaluation of Memory (GEM) Study concluded there was no benefit from ginkgo.

One might question the validity of reporting results from a group that includes 1406 patients who received at least one dose of ginkgo biloba extract and 1414 that received at least one dose of placebo. How can we include people who didn’t take the drug as prescribed?

It’s a good question. However, clinical drug trials are based on results from all who took at least one dose (the intent-to-treat group). It’s considered a more strict criteria. And, if you’re gonna play the game, you gotta know the rules, as these researchers do.

It’s possible the results based on those who took 90% or so of the doses are reported in the text of the article, but the abstract makes no mention of results based on better adherence to treatment.

The risk of bleeding with ginkgo biloba has been a caveat for treating people long term. However, this study did not confirm that concern.

9/6/12 13:38 JR