Cognitive Speed–Accuracy Dissociation in Multiple Myeloma: A Cross‑Sectional Study

Purpose This study examined whether adults with Multiple Myeloma (MM) show measurable cognitive differences compared with neurologically healthy peers. The primary research question focused on identifying domain-specific cognitive deficits and determining whether standard screening tools adequately capture cognitive abilities. Methods A cross-sectional design compared 45 adults with MM to 40 age-matched controls. Participants completed 40–50 minutes of cognitive and psychological assessments, including the Montreal Cognitive Assessment (MoCA), validated measures of mood and daily functioning, and a digitised cognitive battery assessing key cognitive domains. Group differences in reaction time (RTs) and accuracy were analysed using ANCOVAs adjusting for age and education, Bayesian and EZ-drift diffusion modelling (EZ-DDM) to characterise domain specific deficits and latent decision-making processes. Results Group-level analyses revealed slower RTs in MM following adjustment for age and education, with accuracy largely preserved. Bayesian modelling identified multi-domain RT-related deficits in ~ 22% of MM patients, particularly in cognitive flexibility and semantic processing. EZ-DDM indicated that group differences were driven by reduced drift rates and prolonged non-decision times in MM, suggesting slower evidence accumulation with slower sensory encoding and/or motor execution. Conclusion Cognitive slowing in MM is selective and heterogeneous, with processing speed emerging as the most sensitive marker. Conventional screening may underestimated subtle deficits, underscoring the need for longitudinal and neuroimaging studies to disentangle disease and treatment related effects. Preserving processing speed, critical for everyday functioning and social interactions, should be a priority in cancer and chronic disease research.