Early studies in the 1990s, which were broadly embraced by the media and public, reported positive cognitive results from ginkgo supplements. But none of these studies have stood up to scrutiny over time, says Solomon, who co-authored a paper earlier this year in Evaluation & the Health Professions proposing more rigorous guidelines for evaluating the cognitive benefits of alternative medicines.
As for the placebo effect, says DeKosky, it is unlikely to play much of a role in long-term studies like GEM. Rather it is something that researchers are more likely to encounter "very early on" in treatment or short studies. Although the follow-up intervals of this study were not designed to detect such an effect, it is unlikely it would persist for several years, he says. Additionally, notes DeKosky, if patients are thinking about the supplement logically, they wouldn't expect to see results right away. "It wouldn't be logical for a drug that has lots of antioxidants to have a short-term effect of increasing your thinking function. We take them for the longer term."
For his patients, Solomon does not recommend the supplement to treat or prevent Alzheimer's disease or to help with age-related memory problems. DeKosky has similar advice. He notes that "it makes more sense to eat better, exercise and do all of the other things we already know are good for cognitive health" rather than popping unproven pills.
Although DeKosky admits he was disappointed to not find even a hint of help from this herbal supplement, he calls the study itself a success. Recruiting and maintaining such a large group of community-based elderly—and their willing proxies to interview—for six years was no small feat. More of these studies will come, he says, and in the meantime, the research group will continue parsing the data collected from GEM. Next on the list will be to see if the ginkgo had any impact on cardiac disease rates or peripheral vascular disease. The group also plans to image the brains of hundreds of individuals to look for clues and follow some into their late old age.
Solomon, for one, isn't holding his breath for good news from this supplement as a brain booster. "I think it's probably time to throw in the towel for ginkgo," he says. "I think it's time to look for something else."