Effects of almond consumption on sleep quality in adults: a randomized controlled trial.

Mild cognitive impairment (MCI) is widely regarded as an intermediate stage between normal aging and dementia (; ). Longitudinal studies have shown that some individuals with MCI remain cognitively stable over time (stable MCI, sMCI), some progress to dementia (progressive MCI, pMCI), and a considerable proportion may return to normal cognition under appropriate intervention (reversible MCI, rMCI) (). This marked clinical heterogeneity suggests that individuals with MCI may have distinct underlying neuropathological mechanisms. Identifying key factors that shape MCI heterogeneity has therefore become an important issue in cognitive neuroscience and aging research. Neuroticism, a personality trait associated with emotional instability, heightened stress reactivity, and a tendency toward negative affect, has been linked to the risk of cognitive decline, executive dysfunction, and dementia outcomes in older adults (; ; ; ; ; ). Neuroticism may participate in cognitive aging and disease progression and may further influence cognitive and neurophysiological differences among individuals with MCI. From a neurobiological perspective, higher levels of neuroticism are closely associated with chronic activation of the hypothalamic–pituitary–adrenal (HPA) axis (; ). This may subject the prefrontal cortex and hippocampus, areas abundant in glucocorticoid receptors, to sustained elevations in glucocorticoids, consequently compromising synaptic plasticity and neural network integrity, and ultimately heightening the risk of cognitive decline (; ; ; ). Neuroticism is also associated with functional abnormalities in the amygdala-prefrontal network, which may reduce emotion regulation efficiency and executive control (; ). Thus, neuroticism may not only increase the risk of cognitive decline, but also shape the neural processing patterns of individuals with MCI. Working memory is one of the core cognitive components that is vulnerable in the early stage of MCI. Working memory-related EEG markers can sensitively reflect changes in cognitive load in individuals with MCI and distinguish MCI subtypes with different disease trajectories (). Elevated neuroticism may interfere with the maintenance, selection, and updating of task-relevant information by depleting attentional control resources (; ; ). Since visuospatial working memory places particularly high demands on attentional control and executive resources, which are functions known to be affected by neuroticism, it may provide a sensitive task window for detecting neuroticism-related cognitive load effects in MCI. Furthermore, visuospatial working memory has been regarded as a preliminary indicator of the transition from Mild Cognitive Impairment to Alzheimer’s Disease (; ), hence reinforcing its significance in this context.