Gonzalez‐Burgos, Lissett

AbstractBackgroundSubjective cognitive decline (SCD) implies self‐reported cognitive complaints in absence of objective cognitive impairment. SCD has been postulated as an early marker of Alzheimer’s Disease (AD). However, longitudinal studies have linked SCD to future vascular dementia. Thus, we conducted a systematic review and meta‐analysis aiming to synthesise and analyse the available data on the association between SCD and the presence of underlying cerebrovascular pathology measured by MRI.MethodOur study was performed following the PRISMA statement. The search strategy included terms for “subjective cognitive decline” and “white matter signal abnormalities”. It was conducted in 3 databases (PubMed, Scopus and Web of Science) from origin by December 8th, 2021. Two authors screened the studies in a 2‐stepwise approach. Primary studies including cognitively unimpaired adults with subjective cognitive complaints meeting the SCD‐I criteria for SCD that evaluated cerebrovascular pathology based on white matter signal abnormalities (WMSA) on MR images were selected. Study quality was assessed using the FLC 3.0 tool. Meta‐analysis comparing case‐control mean difference of WMSA was performed.ResultOf 240 articles identified, 16 research articles were selected. Of those, 8 case‐control studies were selected for the meta‐analysis. The sample size of the SCD group across the studies ranged from 8 to 906 participants, with age ranged from 40 to 84 years. All eight studies comprised a total of 2.637 SCD individuals. Study quality was deemed moderate (n=6) to high (n=10). The meta‐analysis showed a significant overall effect‐size between the mean WMSA burden of SCD and the controls, that was not significantly heterogeneous (Q(gl=7)=14.20; p=0,04; I2=42,5%). SCD was significantly associated with higher CVP burden based on neuroimaging measures.ConclusionThis is the first study to synthesise and analyse the current evidence on the association between SCD and WMSA. Our findings show the usefulness of SCD as a marker of underlying cerebrovascular pathology. Thus, the potential role of SCD as a preclinical stage of vascular cognitive impairment needs further investigation. Changes in lifestyle (e.g. exercise, diet, smoking cessation), cognitive stimulation or pharmacotherapy may be key to avoid an evolution towards cognitive deterioration in SCD.

AbstractBackgroundSubjective cognitive decline (SCD) in cognitively normal individuals is a relevant predictor of future cognitive decline, dementia, and neurodegeneration. Previous studies showed that the cognitive decline cannot be captured by objective neuropsychological testing in SCD. However, whether sophisticated multivariate approaches such as graph theory can potentially capture subtle cognitive abnormalities in SCD individuals is unknown. This study aimed to assess the cognitive connectome in a relatively large cohort of SCD individuals, in comparison with healthy controls (HC), and assess whether such a connectome differs in SCD across age groups.MethodWe included a total of 390 individuals, of which 211 fulfilled the core SCD criteria proposed by the international SCD Initiative (SCD‐I), and 179 individuals were classified as healthy controls. Participants were stratified into early middle‐age (37–50 years, n = 125), late‐middle‐age (51–64 years, n = 119), and elderly (65–78 years, n = 146) groups. We built cognitive networks from 47 cognitive variables separately for each age and study group using graph theory and compared the groups using global measures of average strength, average global efficiency, average local efficiency, and transitivity.ResultSCD individuals had more segregated networks in all age groups, but more prominently in the late‐middle‐age group. We observed lower within‐module connectivity in SCD individuals, in verbal memory and executive—premotor functions compared with HC. The late middle‐age SCD group showed a pattern of connectivity similar to the elderly HC group. The late‐middle‐age SCD group also showed reduced transitivity compared with the HC. We did not observe significant differences in the rest of the graph measures and in the other groups.ConclusionUsing a sophisticated multivariate approach, we demonstrate that a segregated pattern of cognitive connectivity seems to underlie SCD, particularly in individuals in the age range 51 to 64 years. After the age of 65 years, this pattern tends to be less segregated, contrary to an efficient dedifferentiation process in aging. This, together with subtle signs of brain pathology and other risk factors identified in SCD may increase the likelihood of future cognitive impairment and dementia.