Ginkgo biloba shows no notable effect in reducing the incidence of dementia caused by Alzheimer's disease or dementia overall in older adults when compared with placebo, results of a recent study of more than 3,000 older adults show.
The latest findings are consistent with smaller trials, Beth E. Snitz, Ph.D., and her colleagues reported (JAMA 2009;302:2663–70).
In the current study, adults aged 72–96 years were monitored at six medical centers in the United States between 2000 and 2008 in the largest completed randomized, double-blind, placebo-controlled dementia prevention trial to date, according to Dr. Snitz, of the department of neurology at the University of Pittsburgh, and her colleagues. A total of 60% of subjects successfully completed the study; 54% were men.
Of the total, 1,545 participants were randomized to receive a 120-mg dose of ginkgo biloba extract and 1,524 to receive placebo twice a day, Dr. Snitz noted. Follow-up included neuropsychological testing every 6 months until 2004 and once a year thereafter. The median follow-up was 6.1 years.
The placebo group performed better than did the ginkgo biloba group on 3 of 12 neuropsychological tests administered at baseline. Scores on other tests did not differ by treatment group. The ginkgo biloba and placebo groups did not differ on rates of cognitive change for the global cognition score or cognitive domains tested (memory, attention, visuospatial abilities, language, and executive functions).
In year 6 of the study, a secondary analysis was taken and results were consistent with the primary analysis; rates of cognitive change for the global score and all cognitive domains did not differ by treatment group, the investigators noted. In participants with early dementia or symptoms of cognitive impairment, results also indicated that 3 to 4 years of ginkgo biloba treatment had no significant effect on cognitive decline 2 to 3 years after use.
The clinical meaning of cognitive decline in this study was defined by a 4-point change in the Alzheimer Disease Scale.
“We [found] no evidence that G. biloba slows the rate of cognitive decline in older adults,” wrote the investigators. “These findings are consistent with previous smaller studies examining prevention of decline and facilitation of cognitive performance and with the 2009 Cochrane review of G. biloba for dementia and cognitive impairment.”
Funding for the study was provided in part through a grant from the National Center for Complementary and Alternative Medicine, a division of the National Institutes of Health. Ginkgo biloba extract tablets and placebo tablets were donated by Schwabe Pharmaceuticals.
Dr. Snitz and colleagues reported no relevant conflicts of interest.