The Challenge of Subjective Cognitive Complaints and Executive Functions in Middle-Aged Adults as a Preclinical Stage of Dementia: A Systematic Review

Abstract

Subjective cognitive complaints correspond to a heterogeneous construct that frequently occurs in the early stages of older adult life. Despite being a common source of worry for middle-aged people, it can be underestimated when clinical and neuropsychological assessments discard any underlying pathological processes. Negative age stereotyping but also self-stereotyping can contribute to doing so. Although its diagnosis is a challenge, its implication as a possible predictor of mild cognitive impairment or dementia increases the interest in its early diagnosis and intervention. The present systematic review analyzes the empirical data on the relationship between these complaints and early executive dysfunction with possible predictive value for preclinical stages of dementia. The sixteen papers obtained from the PubMed and Embase databases were exploratory, cross-sectional and prospective in scope. The studies corroborated the relationship between subjective cognitive complaints and some executive processes, which is noteworthy since many people with subjective executive complaints progress to dementia. The relational studies confirmed that impaired executive performance is associated with CSF biomarkers and reduced cortical volume in specific brain regions. However, the heterogeneity of reports in these studies demands stronger efforts in future research with specific tools applied in clinical and neuropsychological assessments and analyzed under a gender perspective.

Preclinical Brain Network Abnormalities in Patients with Subjective Cognitive Decline

“…This may indeed be responsible itself for the cognitive deficits that SCD individuals subjectively experience. Executive dysfunctions have been previously described in SCD populations [32][33][34]. Impairment of higher executive abilities, such as the divided attention or flexibility, may impact on free recall during memory tasks [33,35].…”

The Use of Executive Fluency Tasks to Detect Cognitive Impairment in Individuals with Subjective Cognitive Decline

“…Furthermore, dysexecutive functioning has been reported along the continuum of pathological aging, including MCI and AD [ 34 , 56 ]. The impairment or decline of executive functions has also been reported in SCD, and it is considered an early sign of cognitive decline in pathological aging [ 30 , 34 , 35 , 57 ].…”

“…Impaired executive function is considered an early sign of cognitive decline in the course of pathological aging [ 34 ]. In a recent systematic review, Webster-Cordero and Giménez-Llort found a relationship between cognitive complaints and early impairment of executive functions (i.e., working memory, initiative, cognitive flexibility, inhibition, planning) associated with AD cerebrospinal fluid biomarkers and reduced cortical volume in bilateral hippocampi and left frontal regions [ 35 ].…”

Therapeutic Use and Chronic Abuse of CNS Stimulants and Anabolic Drugs

“…More recently, neuroimaging techniques such as magnetoencephalography (MEG) reflect both learning/memory and executive functions and could be an independent biomarker of cognitive impairment [ 11 ]. This is important because psychiatric comorbidity is often a neglected confounding factor in studies of subjective cognitive complaints [ 12 ].…”