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Background: Subjective cognitive decline (SCD) is the earliest symptomatic manifestation of preclinical Alzheimer's disease (AD). Gut microbiota may serve as a susceptibility factor for AD. Altered gut microbiota has been reported in patients with mild cognitive impairment (MCI) and AD dementia. However, whether gut microbial compositions changed in SCD remains largely unknown.Objective: To characterize the gut microbiota in SCD.Methods: In this study, a total of 105 participants including 38 normal controls (NC), 53 individuals with SCD, and 14 patients with cognitive impairment (CI) were recruited. Gut microbiota of all participants isolated from fecal samples were investigated using 16S ribosomal RNA (rRNA) Illumina Miseq sequencing technique. The gut microbial compositions were compared among the three groups, and the association between altered gut microbiota and cognitive performance was analyzed. To validate the alteration of gut microbiota in SCD, we conducted amyloid positron emission tomography (PET) in selected participants and further compared the gut microbiota among subgroups.Results: The abundance of phylum Firmicutes, class Clostridia, order Clostridiales, family Ruminococcaceae, and genus Faecalibacterium showed a trend toward a progressive decline from NC to SCD and CI. Specifically, the abundance of the anti-inflammatory genus Faecalibacterium was significantly decreased in SCD compared with NC. In addition, altered bacterial taxa among the three groups were associated with cognitive performance. The findings were validated in SCD participants with positive amyloid evidence.Conclusion: The composition of gut microbiota is altered in individuals with SCD. This preliminary study will provide novel insights into the pathophysiological mechanism of AD. [ABSTRACT FROM AUTHOR]

Background: Education plays a potential important effect on the prevalence and incidence of dementia. However, most of the evidence based on convenience sampling.Objective: To explore effects of education on cognition in individuals with subjective cognitive decline (SCD) and cognitive impairment (CI) from a population-based study.Methods: We examined the effect of education on cognition among individuals with SCD (n = 451) and CI (n = 280) from a population-based study. A series of neuropsychological tests of memory, executive, language, and general cognitive function were used to assess the participants.Results: Multiple regression analyses revealed that education has a positive effect on cognition in both SCD and CI group in the population-based research. Further stratification study showed that the beneficial effect of education remains in the SCD group regardless of the education level, especially in the SCD participants with a low education level. However, that effect of education exists in the CI group with a low education level and disappears in the high education level.Conclusion: These results from a population-based sample suggest that high educational attainment may delay cognitive decline in the individuals with SCD regardless of high or low educational level, and high education only predicts cognition in those in the low educational level in CI group. [ABSTRACT FROM AUTHOR]

Background: Accumulating evidence has demonstrated that plasma β-amyloid (Aβ) levels are useful biomarkers to reflect brain amyloidosis and gray matter structure, but little is known about their correlation with subclinical white matter (WM) integrity in individuals at risk of Alzheimer's disease (AD). Here, we investigated the microstructural changes in WM between subjects with low and high plasma Aβ levels among individuals with subjective cognitive decline (SCD). Methods: This study included 142 cognitively normal individuals with SCD who underwent a battery of neuropsychological tests, plasma Aβ measurements, and diffusion tensor imaging (DTI) based on the Sino Longitudinal Study on Cognitive Decline (SILCODE). Using tract-based spatial statistics (TBSS), we compared fractional anisotropy (FA), and mean diffusivity (MD) in WM between subjects with low (N = 71) and high (N = 71) plasma Aβ levels (cut-off: 761.45 pg/ml for Aβ40 and 10.74 pg/ml for Aβ42). Results: We observed significantly decreased FA and increased MD in the high Aβ40 group compared to the low Aβ40 group in various regions, including the body, the genu, and the splenium of the corpus callosum; the superior longitudinal fasciculus; the corona radiata; the thalamic radiation; the external and internal capsules; the inferior fronto-occipital fasciculus; and the sagittal stratum [ p < 0.05, familywise error (FWE) corrected]. Average FA values were associated with poor performance on executive and memory assessments. No significant differences were found in either MD or FA between the low and high Aβ42 groups. Conclusion: Our results suggest that a correlation exists between WM integrity and plasma Aβ40 levels in individuals with SCD. [ABSTRACT FROM AUTHOR]

Background: Subjective cognitive decline (SCD) is considered the earliest symptomatic manifestation of preclinical Alzheimer's disease (AD). Currently, given the lack of effective and curable pharmacological treatments for AD, non-pharmacological interventions (NPIs) for individuals with SCD may provide a valuable opportunity for the secondary prevention of AD.Objective: This systematic review and meta-analysis, conducted in accordance with the PRISMA guidelines, aimed to investigate the benefits of current NPIs in the population with SCD.Methods: The online electronic databases, including MEDLINE, Cochrane Central Register of Controlled Trials, EMBASE, PsycInfo, and CINAHL, were searched to identify randomized controlled trials of NPIs for SCD. Intervention strategies were psychological and health-related education interventions, mind-body therapy, lifestyle modification, cognitive training, and multidomain interventions. Outcomes included subjective memory, objective memory, global cognitive function, psychological well-being, and mood. Study quality was determined using the criteria of the Cochrane collaboration's tool. The Hedges' g of change was analyzed.Results: Eighteen studies were included in this review and meta-analysis. Overall, psychological and health-related education interventions exhibited a medium effect on objective memory function (Hedges' g = 0.53, p = 0.01). Cognitive training led to a small effect on objective memory, which was marginal statistically (Hedges' g = 0.19, p = 0.05). In addition, cognitive training also significantly improved subjective memory performance (Hedges' g = 0.49, p = 0.0003) and psychological well-being (Hedges' g = 0.27, p = 0.03).Conclusion: Overall, the psychological intervention and cognitive training may be beneficial to cognitive function and psychological well-being. NPIs may be effectively implemented in older adults with SCD. [ABSTRACT FROM AUTHOR]