A Cross-sectional Study on Age-Related Changes in Muscle Iron Deposition and Fat Infiltration: Associations with Grip Strength in a Healthy Adult Cohort.

Both the muscle iron content and fat infiltration are associated with sarcopenia. However, the use of magnetic resonance imaging (MRI) for the quantitative assessment of age-related changes in muscle iron content and fat fraction remains limited. This study investigated sex- and age-related differences in muscle iron content and fat fraction in a healthy population, as well as their relationships with handgrip strength (HGS). A total of 198 participants were included. The muscle iron content and fat fraction in the psoas, erector spinae, multifidus, and combined erector spinae and multifidus were determined via the IDEAL-IQ sequence. HGS was evaluated via an electronic handgrip dynamometer. Low HGS was considered if the HGS was < 27 kg for males and 18 kg for females. The muscle iron content and fat fraction increased with age in both men and women (P < 0.01). These variables were negatively correlated with HGS (P < 0.01). The muscle iron content and fat fraction also had acceptable performance in identifying individuals with low HGS (area under the curve (AUC) = 0.673-0.826 for iron content; AUC = 0.818-0.933 for fat fraction). In conclusion, the muscle iron content and fat fraction both increased with age and were both negatively correlated with HGS, which may be used for assessing and screening for sarcopenia.