Abstract
Subjective cognitive decline (SCD) is defined as the presence of self-reported cognitive complaints with unimpaired performance in neuropsychological cognitive tests. SCD has been identified as a precursor of mild cognitive impairment (MCI) and potentially represents the earliest clinical sign of Alzheimer’s disease (AD). Standardized extracts of Ginkgo biloba (GBE) are widely used as a treatment for cognitive impairment. Nonetheless, most of the available review articles focus on the effects of GBE in MCI and dementia but not in SCD and its specific cognitive effects. Thus, this review collects and discusses the available published clinical data for the effects of standardized GBE on the early stages of cognitive decline among an age group where SCD becomes a topic—the middle-aged adults. Randomized clinical trials (RCTs), systematic reviews and meta-analyses of standardized GBEs in cognitive decline subjects were searched using PubMed/MEDLINE, Science direct, Cochrane, and Google Scholar until January 2019. Data from relevant RCT were critically evaluated to determine the potential effects of GBE on SCD. The results showed that the number of available GBE studies on SCD is small. Eight studies were selected in which subjects reported memory impairment, in some cases with concerns (worries), and with an average age at onset SCD of 60 years. Six studies gave a proof of efficacy for GBE for the treatment of SCD in at least one cognitive parameter. One study is inconclusive, however, a post-hoc analysis demonstrates efficacy in preventing AD with intake >4 years. The most common GBE dosage used was 240 mg GBE/day over a minimum period of 8 weeks. Hence, there might be beneficial effects of GBE to prevent, improve or delay SCD in the generation of 50 years or older. However, larger, well-defined RCTs using SCD criteria are necessary to further substantiate this effect in SCD subjects.
Highlights
Our review is based on seven randomized, double-blind, placebo-controlled clinical studies (RCT) and one post hoc analysis [32] of an Randomized clinical trials (RCTs) assessing the effect of oral doses of standardized Ginkgo Biloba Standardized Extract(s) (GBE) in subjects who spontaneously reported memory complaints or age-related cognitive decline
Due to the highly different studies included in this review, a clear conclusion about the necessary treatment duration or the best recommended age to start the intake of standardized GBE in order to prevent dementia cannot been drawn
Apart from one study conducted by Beck and colleagues [33], which followed more closely the Subjective cognitive decline (SCD) and SCD plus criteria features, most of the included studies were published before the SCD definition of Jessen et al, 2014 and have limitations regarding the fulfilment of SCD plus criteria
Summary
In a large population-based study conducted in Germany which included non-demented adults aged 40 - 79 years, the prevalence for memory-related subjective cognitive symptoms was found to be 53.0% [3]. This is in line with similar findings from two other community-based studies conducted in Norway [4] and France [5]. Evidence suggests that SCD may represent the first symptomatic manifestation of Alzheimer’s disease (AD), but it is a common complaint at an older age, independent of AD [2] [6]. In SCD, the apparently felt subtle cognitive decline is not detectable with existing standardized cognition tests, which might be at least partially associated with successful compensation that translates to unimpaired performance levels on individual tests [1]
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