Nine studies were included in the review. These studies related to a total of 1,497 patients. In 2 of the studies, the patients took the intervention for longer than 6 months (1 year and 24 weeks), in the remaining 7 studies, the patients took the intervention for less than 6 months (4 to 12 weeks).
Four of the 9 studies scored the maximum of 5 points on the Jadad score and the remaining 5 scored at least 3 points.
Intervention of 6 months and longer:
Two trials were conducted for longer than 6 months. Both studies showed statistically significant improvements in dementia symptoms in the Ginkgo biloba group compared to placebo, using both a per protocol and intention to treat analysis. For one of these studies at the end of the treatment 28% of the ginkgo group and 10% of the placebo group had responded to treatment, the authors do not report figures for the other trial. Both trials found a greater response in Alzheimer patients than in multi-infarct dementia patients.
There did not appear to be an association with adverse effects and Ginkgo biloba in either of the studies. In one of the studies 16% and 12% of patients attributed adverse effects to Ginkgo biloba or placebo respectively. In the other study a causal relationship between Ginkgo biloba and serious adverse effects was ruled out by the authors with the exception of a patient who suffered a suspected acute stroke.
Intervention of less than 6 months:
7 studies with a duration of less than 6 months assessed the effect of Ginkgo biloba on dementia. All 7 studies suggested a greater benefit of Ginkgo biloba compared to placebo and this difference was statistically significant in 6 of the 7 studies. Two of the studies reported on adverse effects and neither of these studies found a greater incidence of adverse effects in the Ginkgo biloba group.