Herbal-Based Products in the Treatment of Subjective Cognitive Decline in the Elderly: A Literature Review
Subjective cognitive decline (SCD) is a self-perceived worsening of cognitive functioning, particularly in the memory domain, which cannot be verified by neuropsychological tests.
SCD lies on a continuum of healthy cognitive aging and is conceptualized as the preclinical phase of dementia (from healthy cognitive aging, through preclinical SCD, followed by prodromal mild cognitive impairment (MCI), and then dementia).
SCD is estimated to double the risk of future objective decline (MCI or dementia), leading to a higher prevalence of Alzheimer’s disease biomarkers and impacting mental health (1 in 3 individuals) and functional capacity (1 in 2 individuals).
The prevalence of SCD is estimated to be 1 in 4 older adults aged 60 and above worldwide, with the number increasing rapidly each year.
Currently, there are no approved pharmacological interventions, and many older adults affected by subjective cognitive decline seek alternative treatments.
The difficulty also lies in assessing subjective cognitive decline since current diagnostic tools have been developed for MCI or dementia.
Moreover, there are inconsistencies in the categorization of SCD in research (especially the division between healthy adults without SCD and those with SCD). Due to the increased risk of dementia and the high prevalence of SCD, high-quality research on effective treatments to improve cognitive functioning and delay further decline is needed.
A review and meta-analysis conducted in 2018 examined various interventions (group psychological, cognitive, lifestyle, and complementary and alternative medicine) for the treatment of subjective cognitive decline and their effectiveness on psychological well-being, metacognition, and objective cognitive performance.
The authors found that the studies were generally of low quality, making it impossible to draw definitive conclusions about the effectiveness of the interventions used. Although this review/meta-analysis is crucial for advancing research on SCD treatment, it did not explore the effectiveness of individual interventions on cognitive functioning, nor did it investigate the use and efficacy in older adults without SCD.
Complementary medicines (CM) are defined as a wide range of healthcare approaches not considered part of conventional medical care.
Complementary medicines are classified into three main categories: nutritional (e.g., herbs, dietary supplements), psychological (e.g., meditation, relaxation therapy), and physical (e.g., acupuncture, massage).
Health supplements are becoming increasingly available and used by older adults, particularly herbal and nutritional medicines for the treatment of chronic health conditions, including cardiovascular diseases, diabetes, and dementia.
Herbal medications contain substances or herbal preparations, while nutritional/medicinal supplements contain vitamins, minerals, and combined formulas with herbal substances/preparations. The natural properties of these medications make them appealing to individuals seeking to improve their health and overall well-being.
Background
The primary aim of this review was to investigate the effectiveness of herbal and nutritional medicines on cognitive function and safety (compared to an appropriate control group) for older adults with and without subjective cognitive decline. Secondary objectives included describing the study characteristics and assessing the methodological quality of included studies using the Cochrane risk of methodological bias (ROB 2) tool.
Method
Five databases (Cochrane, MEDLINE, CINAHL, PsycInfo, and EMBASE) were searched from the inception of the databases with weekly alerts until the review’s completion on September 18, 2022. Eligible articles included the following elements: study population of older adults with and without subjective cognitive decline, herbal and nutritional medicines as the intervention, assessment of cognitive outcomes, and randomized controlled trials.
Results
Data were extracted from 21 out of 7666 eligible full-text articles, and the risk of methodological bias was assessed (with SCD = 9/21; without SCD = 12/21). Most studies (20/21) used parallel, randomized, placebo-controlled designs with a duration of 12 weeks. Herbal supplements were widely used (17/21), particularly a form of Ginkgo biloba (8/21) or Bacopa monnieri (6/21).
Cognition measures varied across studies, with 14/21 reporting improvements in at least one cognitive functioning domain over time in the intervention group (compared to the control group). A total of 14/21 studies were considered at high risk of methodological bias, 6/21 had some concerns, and only one study (utilizing an SCD population) was rated as low risk of methodological bias.
Conclusions
Overall, this review found low-quality evidence regarding the effectiveness of herbal and nutritional medicines on cognitive function and safety for older adults with and without subjective cognitive decline, due to a high risk of bias among studies.
Furthermore, further work is needed on the classification and understanding of subjective cognitive decline and the selection of primary outcomes in studies before future research can more accurately determine the effectiveness of interventions for this population.
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Source: Cave AE, Chang DH, Münch GW, Steiner-Lim GZ. A systematic review of the safety and efficacy on cognitive function of herbal and nutritional medicines in older adults with and without subjective cognitive impairment. Syst Rev. 2023 Aug 17;12(1):143.
