Vasodilators and Nootropics as Predictors of Dementia and Mortality in the PAQUID Cohort
To assess the effects of treatment for memory impairment and the Ginkgo biloba extract (EGb 761) on dementia, mortality, and survival without dementia.
Prospective community-based cohort study.
Three thousand five hundred thirty-four subjects aged 65 and older.
Information on drug consumption was obtained by interview and visual assessment of patients' medicine chests. Active screening of dementia was performed every 2 years over a 13-year period. The independent effects of treatment for memory impairment and the Ginkgo biloba extract on the risks of dementia and death were estimated using Cox proportional hazards models, adjusted for potentially confounding factors (including comorbidities).
The initial consumption of Ginkgo biloba did not modify the risk of dementia (relative risk (RR)=1.16, 95% confidence interval (CI)=0.84-1.60), whereas the consumption of other treatments for memory impairment was associated with a higher risk of dementia (RR=1.35, 95% CI=1.11-1.63). Subjects who took Ginkgo biloba had a significantly lower risk of mortality in the long term (RR=0.76, 95% CI=0.62-0.93), even after adjustment for potentially confounding factors. The initial consumption of treatment for memory impairment other than Ginkgo biloba did not modify the risk of mortality.
These results suggest that treatment with EGb 761 may increase the probability of survival in the elderly population. These findings need to be corroborated and further assessed using randomized, controlled trials.
Available from: Jan Kehr
- "Based on the evidence from randomized and controlled clinical trials, the German Institute for Quality and Efficacy in Health Care (IQWiG) concluded that EGb 761 R is beneficial in AD (IQWiG, 2008). Two large-scale prospective cohort studies have suggested that long-term intake of EGb 761 R might protect against development of dementia (Andrieu et al., 2003; Dartigues et al., 2007). A randomized placebo controlled pilot study highlighted that delay of conversion to dementia can only be expected with good compliance in long-term treatment (Dodge et al., 2008).The Ginkgo Evaluation of Memory (GEM) study was carried out to test whether Ginkgo biloba is effective in prevention of dementia (and especially AD) in elderly individuals with normal cognition or those with mild cognitive impairment (DeKosky et al., 2008). "
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ABSTRACT: Experimental and clinical data suggest that the Ginkgo biloba standardized extract EGb 761® exerts beneficial effects in conditions which are associated with impaired cognitive function. However, the neurochemical correlates of these memory enhancing effects are not yet fully clarified. The aim of this study was to examine the effect of repeated oral administration of EGb 761® and some of its characteristic constituents on extracellular levels of dopamine (DA), noradrenaline (NA), serotonin (5-HT), acetylcholine (ACh) and the metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA) in the medial prefrontal cortex (mPFC) of awake rats by use of in vivo microdialysis technique. Subacute (14 days, once daily), but not acute, oral treatment with EGb 761® (100 and 300 mg/kg) or the flavonoid fraction, which represents about 24% of the whole extract caused a significant and dose-dependent increase in extracellular DA levels in the mPFC. Repeated administration of EGb 761® also caused a modest but significant increase in the NA levels, whereas the concentrations of 5-HT and those of the metabolites DOPAC, HVA and 5-HIAA were not affected. The same treatment regimen was used in a subsequent study with the aim of investigating the effects of two Ginkgo-specific acylated flavonols, 3-O-(2''-O-(6'''-O-(p-hydroxy-trans-cinnamoyl)-β-D-glucosyl)-α-L-rhamnosyl)quercetin (Q-ag) and 3-O-(2''-O-(6'''-O-(p-hydroxy-trans-cinnamoyl)-β-D-glucosyl)-α-L-rhamnosyl)kaempferol (K-ag). Both compounds together represent about 4.5% of the whole extract. Repeated oral treatment with Q-ag (10 mg/kg) for 14 days caused a significant increase in extracellular DA levels of 159% and extracellular acetylcholine (ACh) levels of 151% compared to controls. Similarly, administration of K-ag (10 mg/kg) induced a significant rise of DA levels to 142% and ACh levels to 165% of controls, whereas treatment with isorhamnetin, an O-methylated aglycon component of EGb 761® flavonol glycosides had no effect. None of the tested flavonoids had a significant effect on extracellular DOPAC and HVA levels. The present findings provide evidence that the subacute treatment with EGb 761® and its flavonol constituents increases DA and ACh release in the rat mPFC, and suggest that the two Ginkgo-specific acylated flavonol glycosides Q-ag and K-ag are active constituents contributing to these effects. As seen for isorhamnetin, the effect on neurotransmitter levels seems not to be a general effect of flavonols but rather to be a specific action of acylated flavonol glycosides which are present in EGb 761®. The direct involvement of these two flavonol derivatives in the increase of dopaminergic and cholinergic neurotransmission in the prefrontal cortex may be one of the underlying mechanisms behind the reported effects of EGb 761® on the improvement of cognitive function.
Available from: Satomi Kagota
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ABSTRACT: We previously demonstrated that Ginkgo biloba extract (GBE) produces an anti-hypertensive effect via enhanced vasodilation responses in young spontaneously hypertensive rats (SHR) and hepatic hypertrophy occurs with increased cytochrome P450 (CYP) mRNA expression in young rats. In the present study, to clarify whether these actions of GBE are observed in older rats, we investigated cardiovascular functions and hepatic CYP protein expressions in aged SHR fed a control diet or a diet containing 0.5% GBE for 4 weeks. In aged SHR, GBE feeding significantly increased liver weight per 100 g body weight without changing the body weight. Furthermore, significant increases in alanine aminotransferase level in serum and marked increase in CYP2B protein expression in the liver were observed in aged SHR fed GBE. On the other hand, GBE feeding did not affect blood pressure, but significantly reduced heart rate and blood flow velocity in tail arteries of aged SHR. Furthermore, GBE feeding did not affect contractile response to phenylephrine, relaxation responses to not only sodium nitroprusside but also acetylcholine, and protein levels of endothelium nitric oxide synthase and soluble guanylate cyclase in aortas of aged SHR. These results suggested that long-term GBE feeding impairs peripheral circulation due to bradycardia and hepatic function in aged SHR. Thus, in the elderly population with hypertension, the use of GBE may need to be assessed for effects on heart rate and liver function.
Available from: Nicola Coley
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ABSTRACT: The prevention of neurodegenerative dementias, such as Alzheimer disease, is a growing public health concern, because of a lack of effective curative treatment options and a rising global prevalence. Various potential risk or preventive factors have been suggested by epidemiologic research, including modifiable lifestyle factors, such as social contacts, leisure activities, physical exercise, and diet, as well as some preventive pharmacologic strategies, such as hormone replacement therapy, nonsteroidal antiinflammatory drugs, and Ginkgo biloba. Some factors have been targeted by interventions tested in randomized controlled trials, but many of the results are in conflict with observational evidence. The aim of this paper is to review the epidemiologic data linking potential protective factors to dementia or cognitive decline and to discuss the methodological limitations that could explain conflicting results. A thorough review of the literature suggests that, even if there are consistent findings from large observational studies regarding preventive or risk factors for dementia, few randomized controlled trials have been designed specifically to prove the protective effects of interventions based on such factors on dementia incidence. Because of the multifactorial origin of dementia, it appears that multidomain interventions could be a suitable candidate for preventive interventions, but designing such trials remains very challenging for researchers.
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