Research on Ginkgo biloba products

Together with researchers at the Technical University of Berlin (TU Berlin), IQWiG researchers carried out an assessment of Ginkgo-based products. These herbal preparations are made from the leaves of the Ginkgo biloba tree. They are believed to have various benefits, such as improving blood circulation and protecting nerve cells. Ginkgo products are available without a prescription. In Germany, they can also be prescribed by doctors for people who have Alzheimer’s disease.

In order to find out whether people who have Alzheimer’s disease really benefit from Ginkgo-based products, IQWiG analysed all of the good quality trials in this area. In these trials, people with Alzheimer’s disease were randomly assigned to two or more groups and given either Ginkgo, a fake medication (placebo) or a different medication. All of these randomised controlled trials were “blinded”. This means that neither the participants nor their doctors knew which of the preparations they were taking.

The IQWiG researchers included seven trials in their analysis, involving just under 1,800 participants. Six of the trials compared Ginkgo to a placebo, and one trial compared it to a dementia medication (donepezil). But this trial could not deliver definitive results about how these two medications compare to one another.

All of the trials tested a specific Ginkgo preparation based on the extract EGb 761. The IQWiG researchers could not find any good quality trials of other Ginkgo-based preparations. The doses that were tested were 120 mg and 240 mg per day. Apart from one of the trials, they were all funded by the manufacturer of the Ginkgo extract.

The participants all had mild to moderate Alzheimer’s disease, but there were quite big differences between the trials otherwise. For example, the average age of the participants was 65 in some trials and 78 in others. There were also big differences between the trials in terms of the symptoms that the participants had: for example, some trials mainly included people who had experienced mental changes caused by Alzheimer’s disease, such as restlessness and depression.

The trials all tested whether the Ginkgo extract improved people’s ability to remember things and whether it helped them to carry out daily activities again, such as shopping, washing themselves or doing household chores. Most of the trials also looked at whether the extract reduced psychological symptoms that accompany dementia, such as depression or hallucinations. Other important aspects, like the quality of life of participants and their relatives, were only considered in a few of the trials.

High doses of Ginkgo extract EGb 761 could make everyday life easier

The trials showed that people who took the higher dose of the Ginkgo extract (240 mg per day) were better able to perform daily activities again, like household chores or washing themselves. However, this effect was not equally big across all of the trials, so it is not possible to be sure about how many people could benefit from Ginkgo and how strong its effect is. The lower dose of the Ginkgo extract (120 mg per day) did not have a clear effect on the symptoms of Alzheimer’s disease.

The extract may have a stronger benefit in younger patients or those who have psychological problems caused by Alzheimer’s disease, but it is not possible to know for sure at this stage.

The trials also indicated that, when taken in high doses, Ginkgo could reduce psychological symptoms and improve people’s ability to remember things. It also seemed to reduce emotional stress for caregiving relatives. Further research is needed to be sure of this, though.

Adverse effects are not common and interactions cannot be ruled out

Most of the adverse effects that are associated with other anti-dementia drugs were not more common in people who took Ginkgo than they were in people who took a placebo. But patients often stopped taking Ginkgo due to adverse effects anyway.

It cannot be ruled out that Ginkgo may interact with other drugs. There have been rare reports that it increases the effect of blood-thinning medications like ASS (acetylsalicylic acid, eg Aspirin) and warfarin. So it is important to let doctors know about all of the medicines that are being taken as well as Ginkgo.

You can read more about using herbal products here.

Note

This health information is a summary of a scientific report published by IQWiG. It is not an assessment of the right to have health care services reimbursed by statutory health insurance funds in Germany. By law, decisions about the reimbursement of diagnostic and therapeutic procedures can only be made by the German Federal Joint Committee (G-BA). The Federal Joint Committee takes IQWiG reports into consideration in its decision-making process. You can find information about the decisions of the German Federal Joint Committee on its English-language website, www.english.g-ba.de.

References

• German Institute for Quality and Efficiency in Health Care (IQWiG). Ginkgo in Alzheimer’s disease. Final report A05-19B. Version 1.0. Cologne: IQWiG. September 2008. [Executive summary] [Full text – in German]