Ginkgo biloba extract EGb 761 in dementia: intent-to-treat analyses of a 24-week, multi-center, double-blind, placebo-controlled, randomized trial

In 1996, Kanowski et al. reported about the beneficial effects of ginkgo biloba special extract EGb 761 (240 mg/day) in outpatients with pre-senile and senile primary degenerative dementia of the Alzheimer type (DAT) and multi-infarct dementia (MID) of mild to moderate severity. The comparison of the results of this double-blind, placebo-controlled, randomized, multi-center study with other dementia studies is hampered by the fact that only the responder analysis of the per-protocol (PP) population, which was pre-specified in the protocol as confirmatory analysis, has been published in detail so far. Moreover, cognitive functioning was measured using the Syndrom-Kurztest (SKT), whereas results of other studies are based on the Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-cog). Therefore, the conventional intention-to-treat (ITT) analysis of this study is provided with an estimation of ADAS-cog scores based on measured SKT scores. After 24 weeks of treatment, the ITT analysis of the SKT and estimated ADAS-cog scores revealed a mean decrease in the total score by -2.1 (95 % CI: -2.7; -1.5) points and -2.7 (95 % CI: -3.5; -1.9) points, respectively, for the EGb 761 group, which indicates an improvement in cognitive function. On the contrary, the placebo group exhibited only a minimal change of -1.0 (95 % CI: -1.6; -0.3) and -1.3 (95 % CI: -2.0; -0.4) points, respectively. The changes from baseline differed significantly between treatment groups by 1.1 (SKT) and 1.4 (estimated ADAS-cog) points, respectively (P = 0.01). The Clinical Global Impression of Change (CGI, Item 2) favored the EGb 761 group with a mean difference of 0.4 points (P = 0.007). Changes in the rating related to activities of daily living (Nürnberger-Alters-Beobachtungs-Skala, NAB) showed a favorable trend for EGb 761R. A subgroup analysis regarding patients with DAT yielded comparable results. Using a decrease of at least 4 points on the estimated ADAS-cog scores as cutoff criterion for treatment response, 35 % of EGb 761-treated patients were considered responders versus only 19 % for the placebo group (P = 0.01). The results of this ITT analysis substantiate the outcomes previously obtained with a responder analysis of the per-protocol population and confirm that EGb 761 improves cognitive function in a clinically relevant manner in patients suffering from dementia. The therapeutic effect is in line with the outcome of another EGb 761 study conducted in the U.S.