A few years ago I called a woman whose husband I was treating. I told her I wanted to refer him to a neurologist. "For his back?" she questioned. "No," I answered. "I am worried about his memory." (In fact, I was worried about Alzheimer's.) After a long pause, she said, "I have been too.
Ginkgo Biloba
For quite a few years, ginkgo biloba has been promoted as a natural treatment to prevent or, in most cases, at least retard the progression of Alzheimer's disease. The literature supporting its use has been inconsistent. Alternative practitioners in the complementary health professions tends to emphasize and gravitate toward the positive studies, while traditional mainstream medicine tends to be more skeptical of smaller studies from less prestigious journals and point to the larger analyses, like the review of 36 studies comprising over 4,400 people with mental function loss. In that paper, the authors could not determine if ginkgo biloba was effective, although they did confirm its safety.1
Ginkgo and Memory: What the Latest Research Says
The Ginkgo Evaluation of Memory Study involved more than 3,000 subjects with a mean age of 79 years.2 The National Center for Complementary and Alternative Medicine and the Office of Dietary Supplements were the primary sponsors of this double-blind study. Both alternative and allopathic practitioners were anticipating the results. Subjects were given 240 mg of ginkgo biloba extract (120 mg b.i.d.), standardized to contain 24 percent ginkgo-specific flavone glycosides and 6 percent terpene lactones; or a placebo in the same packaging and taken in the same manner. The trial ran from 2000 until 2008 with a median follow-up time of six years.
Exclusion criteria included those with marked dementia, current use of antidepressants, low vitamin B12 levels and thyroid disease. Subjects with mild cognitive impairment based on published guidelines3 were not excluded. They comprised 15 percent of the 1,524 placebo takers and 16.5 percent of the 1,545 test subjects.
Participants received a battery of tests at baseline and took the Modified Mini-Mental State examination and Alzheimer's Disease Assessment Scale test every six months until 2004, and then annually along with 10 other neuropsychological tests. The results of the study are presented in Table 1. The scores are tabulated from numerous tests done by the authors. The smaller score indicates a slower rate of decline, which is a more favorable outcome.
| The Ginkgo Evaluation Of Memory Study: Neuropsychological Test Score Decline Rates* | |||
| Test Category | Placebo | Ginkgo Biloba | Most Effective |
| Memory | 0.041 | 0.043 | Placebo |
| Attention | 0.048 | 0.043 | Ginkgo |
| Visuospatial | 0.118 | 0.107 | Ginkgo |
| Language | 0.041 | 0.045 | Placebo |
| Executive function | 0.089 | 0.092 | Placebo |
| Cognition | 0.071 | 0.069 | Ginkgo |
| *Lower test scores indicate slower rates of decline or a more favorable outcome in terms of disease progression. | |||
Alzheimer's: A Brief Review
Alzheimer's is a degenerative brain disease. It is the most common cause of dementia (memory loss, confusion and difficulty with speech, judgment and emotions) by a wide margin. Very simplified overviews of the two mechanisms of the disease process are as follows:
- The first feature of the Alzheimer's disease process causes harm outside the cells of the brain. Amyloid precursor proteins (APP) are found in the synapses of neurons. They are on the cell membranes and could be described as hair-type structures which, under normal conditions, help nerve cells grow and repair. In Alzheimer's disease, something activates enzymes that cut these proteins like scissors cut hair. The cuttings are protein fragments known as beta-amyloid. They begin to coalesce and form insoluble plaque which proliferates around blood vessels and nerve cells in the brain, causing compression and atrophy of vital structures.
- Alzheimer's disease has a second pathological process that harms the inside of nerve cells. Tau proteins normally stabilize intraneuronal structures. Something triggers their regulatory enzymes to become overactive. This changes the shape of Tau proteins, which leads to the formation of neurofibrillary tangles, which destroys the inside of the cell.
The result of this unfortunate process is mild memory loss progressing to significant memory loss along with other neuropsychological symptoms, including confusion, learning difficulties, mood swings, personality changes and progressive cognitive dysfunction. It is a devastating disease to witness and a problem that is growing around the world.
Comment
In the largest, longest trial on ginkgo biloba and neurocognitive decline to date, the results were unimpressive to some and disappointing to others. If you have a patient, family member or friend with Alzheimer's disease and ginkgo helps them, keep giving it. Because of the money involved, there will probably be a pushback from those who manufacture, market and sell ginkgo. Rather than make accusations or claim conspiracy, I hope those who profit from sales will use their profits to fund more studies to either confirm or refute the findings of this one. And it is important to remember that failure to reduce mental decline does not mean ginkgo will be ineffective for its other proposed, less publicized applications.
References
- Birks J, Evans JG. Ginkgo biloba for positive impairment and dementia. Cochrane Database of Systematic Reviews, 2009;(1):CD003120.
- Snitz BE, O'Meara ES, Carlson MC, et al. Ginkgo biloba for preventing cognitive decline in older adults. JAMA, 2009;302(24): 2663-2670.
- Winblad B, Palmer K, Kibipelto M, et al. Mild cognitive impairment: report of the International Working Group on Mild Cognitive Impairment. J Intern Med, 2004;256(3):240-246.
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