Associations of Elevated Red Cell Distribution Width (RDW) with Decreased Physical and Cognitive Function in Older Adults, and The Potential Mediation by Mitochondrial Energetics: The Study of Muscle, Mobility and Aging (SOMMA).

We analyzed the association between RDW and skeletal muscle mitochondrial energetics and how skeletal muscle mitochondrial energetics may mediate the associations of RDW with physical and cognitive performance. The study analyzed cross-sectional baseline data from the Study of Muscle, Mobility and Aging (SOMMA) that enrolled 864 participants aged 70 and older (mean=76.3 years). RDW, clinical and demographic parameters were assessed. Comprehensive evaluations were conducted for both physical and cognitive function using objective and subjective measures. Elevated RDW values were significantly correlated with decreased physical performance, evidenced by reduced cardiorespiratory fitness (VO2peak) and longer time to 400 m Walk, alongside impaired cognitive performance. Higher RDW values also demonstrated robust negative associations with various measurements of mitochondrial energetics, including maximal ATP production and oxidative phosphorylation. Mediation analysis revealed that impaired mitochondrial function partly mediated the associations between RDW values and VO2peak, and other physical and cognitive performance. These findings suggest that higher RDW is associated with declines in various physical and cognitive performance, with skeletal muscle mitochondrial energetics serving as a potential mediating factor. Causal inferences about potential mediation are limited by the cross-sectional design of the study. Nevertheless, the findings highlight the value of RDW as a potential biomarker for age-related declines in physical and cognitive function partly mediated by mitochondrial energetics.