Could Subjective Cognitive Complaints Give the Facts of Objective Cognitive Impairments in Non-Central Nervous System Cancer? A Systematic Review.

INTRODUCTION: Non-central nervous system (non-CNS) cancer patients experienced cognitive impairment, both subjectively and objectively. However, they are only weakly correlated. Previous studies indicated that subjective cognitive complaints (SCCs) could be a distinct neural phenotype from objective neuropsychological function. To explore what underlies SCCs, we examined the relationship between SCCs and objective neuropsychological assessment in this systematic review. METHODS: Following the PRISMA guidelines, we searched multiple databases from September 2000 to November 2024 for cross-sectional studies that directly investigated SCCs and neuropsychological assessment, excluding those involving neurological conditions. Sixteen of the 202 articles met the criteria; the total sample included 2093. We used multilevel meta-analysis in R to analyze 156 correlation coefficients and estimated the sampling error variance, within-study variance, and between-study variance from the analysis. RESULTS: The correlations between SCCs and objective neuropsychological examinations were low but significant. When using cognitive domains, female ratio, and age disparity as variables, 57.18% of the variance was attributed to within-study variance. As the female ratio increased, correlations between SCCs and executive function were inconsistent but consistent with attention and memory. When considering the relationship with age disparity, the trend would be corrected. CONCLUSIONS: Different cognitive domains may show distinct trends, suggesting that neuropsychological functions can be predicted by SCCs when controlling for specific conditions. Potential mechanisms include hormonal influences, age-related biological and psychosocial changes, and differences in emotional vulnerability across the lifespan. The present study highlights the importance of carefully evaluating subjective cognitive complaints within evidence-based decision-making processes.