Masseter Muscle Volume and Its Association with Sarcopenia and Muscle Determinants with Insights from ACTN3 Polymorphism in Older Japanese Adults: the Bunkyo Health Study

AimSarcopenia has been associated with a decrease in masseter muscle (MM) thickness in high-risk older populations. However, the relationship to sarcopenia and determinants of MM volume (MMV) in the general older population remain unclear. MabethodIn a cross-sectional study of 1484 older adults of Tokyo, we evaluated MMV using 3D MRI scanning, appendicular skeletal muscle mass (ASMM), handgrip strength, dietary intake, smoking, insulin-like growth factor 1 (IGF-1) levels, and the ACTN3 R577X polymorphism. Participants were divided into quintiles based on MMV (Q1-5). ResultsOur study of participants with a mean age of 73.0 {+/-} 5.3 years, MMV (Men:35.3 {+/-} 7.8 ml, Women: 25.0 {+/-} 5.1 ml) was significantly larger in men than in women. A significant association between MMV and sarcopenia was observed, with the lowest quintile (Q1) showing a higher risk compared to the highest quintile (Q5) in both sexes. Body mass index (BMI) and age were independent determinants of ASMM in both sexes, while BMI, but interestingly not age, was a determinant of MMV. Moreover, IGF-1 was positively correlated with MMV in both sexes; smoking negatively correlated with MMV in women. The ACTN3 577X polymorphism was associated with only smaller MMV in men. ConclusionLow MMV increased the risk of sarcopenia, particularly in men. BMI and age strongly influenced ASMM, while MMV was only weakly associated with BMI and not with age. Notably, the IGF-1 level was positively correlated to only MMV, and the ACTN3 genotype was linked to reduced only MMV in men.