Association of decreased hemoglobin levels with worse muscle mass and strength in community-dwelling older people

We investigated the associations between red blood cell (RBC) count, hemoglobin (Hb) levels, muscle properties, and muscle strength in community-dwelling older adults, and examined whether RBC count and Hb levels were linked to muscle strength through muscle mass and/or quality, and whether these relationships were influenced by physical activity. The study included 85 community-dwelling older adults (39 males; mean age 75.3 ± 6.7 years). The participants visited the laboratory in the morning for venous blood sampling to analyze blood biomarkers. Quadriceps femoris muscle thickness (MT, muscle mass index) and echo intensity (EI, muscle quality index) were measured via B-mode ultrasonography, and maximum isometric knee extension strength was assessed using a dynamometer. The average daily step count was recorded for 2 weeks as an index of physical activity. Correlation and mediation analyses were used to investigate the associations between blood biomarkers and muscle properties, strength, and physical activity. The RBC count and Hb levels were positively correlated with MT and muscle strength, and negatively correlated with EI. After adjusting for age and sex, the correlations between RBC count, Hb levels, and MT and muscle strength remained significant, whereas the associations with EI disappeared. In the mediation analyses, the direct effect of RBC count and Hb levels on muscle strength was not significant, whereas the indirect effect of MT was, regardless of whether physical activity was adjusted. In community-dwelling older adults, lower RBC counts and Hb levels appear to be associated with diminished muscle mass, potentially resulting in muscle weakness.