The Cognitive Connectome in SCD

Abstract

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.