Gingko extract improves cognitive performance, social function in patients with dementia, according to JAMA study.

Health News Daily via Individual Inc. : GINGKO BILOBA EXTRACT IMPROVES MENTAL PERFORMANCE of individuals with Alzheimer's disease and multi-infarct dementia, researchers report in a placebo-controlled, double-blind, randomized study published in the Oct. 22 issue of the Journal of the American Medical Association.  

Based on the results of the 52-week trial, ginkgo biloba leaf extract (EGb 761) "appears to stabilize and, in an additional 20% of cases (vs. placebo), improve patient's functioning for periods of six months to a year," Pierre Le Bars, MD/PhD, New York Institute for Medical Research, et al. stated.  

Although ginkgo biloba has been extensively studied in Europe, "no empirical trials" of the extract had been conducted in the U.S. As a result, Le Bars and colleagues undertook the multi-center trial "to assess the efficacy and the safety of EGb in AD and multi-infarct dementia (MID). " Of 549 patients screened, 327 sufferers of mild to moderately severe dementia were randomized. Inclusion criteria required that patients not have other significant medical conditions, such as cardiac or liver disease, and that patients taking medication "known to affect cognitive function" would not be permitted to alter their regimens.  

Following a 14-day single-blind placebo run-in period, patients were randomized to either placebo or EGb, a 40 mg standardized tablet "to be swallowed before each of the three principal daily meals for a total dose of 120 mg. " Assessments of adverse events and vital signs, as well as pill counts and drug dispensation, were conducted at 4, 12, 26, and 52 weeks. Primary outcome measures were assessed at baseline and weeks 12, 26 and 52.  

The primary outcome measures assessed changes in three areas. Cognitive impairment was gauged by cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-Cog), "a performance-based cognitive test that objectively evaluates memory, language, praxis, and orientation," using 11 items which are scored 0-70 (higher scores correlating to poorer performance). Daily living and social behavior was assessed by the Geriatric Evaluation by Relative's Rating Instrument (GERRI), "a 49-item rating inventory completed by the care-giver." General psychopathology was measured using the Clinical Global Impression of Change (CGIC), "an interview-based global rating that quantifies the clinician's judgment of the amount of change in overall impairment compared that at the study baseline."  

An intent-to-treat (ITT) analysis "with last observation carried forward " was initially designed to serve as a secondary analysis, but due to "the relatively low proportion of patients completing the entire study and their unequal distribution between the treatment arms, the ITT analysis was selected a posteriori as the primary analysis for efficacy," Le Bars notes. Of the total 327 enrollees, 309 patients were included in the ITT analysis. "Of the 244 ITT patients reaching the 26-week visit, 202 (97 for EGb and 105 for placebo) provided evaluable data and could be included in the evaluable end point analysis," the authors say.  

Using the ADAS-Cog test, the ITT analysis revealed "no significant change observed at end point for the EGb group, whereas the placebo group showed a significant worsening of 1.5 points (P=.006)." As a result, "the mean treatment difference significantly favored EGb (P=.04)," the researchers report. Based on the GERRI scoring, "mild improvement was observed for the EGb group, whereas the placebo group showed significant worsening (0.08 points; P=.02), resulting in a statistically significant difference in favor of EGb (P=.004)." The CGIC did not detect a significant difference between the groups.  

When examined separately, the Alzheimer's subgroup demonstrated significant changes in both ADAS-Cog (P=.02) and the GERRI (P=.001). Significant improvements were also seen in the evaluable population (those completing to the point of analysis) with EGb scores bettering placebo for ADAS-Cog week 26 (P=.04) and week 52 (P=.005) and in the GERRI week 26 (P=.04) and week 52 (P=.002).  

According to a categorical analysis of positive and negative outcomes, ginkgo biloba extract "shows a higher percentage of `improvers', while the placebo shows more `decliners'," Le Bars and colleagues state. On the ADAS-Cog, 50% of the EGb group demonstrated improvement by at least two points compared to 29% among placebo takers. This ratio was the same among those making four-point gains (a four point gain being equivalent to a six-month delay in the progression of the disease). "On the GERRI, 37% of EGb were considered improved and only 19% were considered worse; the placebo group demonstrated the opposite trend with 40% worsening and 23% improving," the study notes.  

Multiple compounds contained in the EGb extract are "thought to act synergistically on diverse processes involved in the homeostasis of inflammation and oxidative stress, providing membrane protection and neurotransmission modulation, which may be the basis for EGb effects at the central nervous system," the authors note, concluding "further research is needed to elucidate the precise mechanism of action of EGb, to fully explore the therapeutic potential of this plant extract and to help better understand the pathogenesis of dementia."  

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