The Gut Microbiota Genus Blautia is Associated with Skeletal Muscle Mass Reduction in Community-Dwelling Older Japanese Adults: The Wakayama Study

Purpose: This cross-sectional study examined the gut microbiota species associated with skeletal muscle mass reduction in a community-based sample of older Japanese adults. Methods: The study included 744 participants aged 65–89 years (mean age, 73 years) with no history of treatment for colorectal, chronic kidney, or liver diseases. Bioelectrical impedance analysis was performed to estimate the appendicular skeletal muscle mass (ASM) of each participant. The gut microbiota composition was assessed using next-generation sequencing targeting the V3-V4 regions of the prokaryotic 16S rRNA genes. A self-administered questionnaire was used to evaluate daily living habits, including food intake associated with maintaining the gut microbiota. Results: Among the participants, those with reduced muscle mass (defined as an ASM index of less than 4.4 kg/m² for men and 3.7 kg/m² for women) had significantly higher levels of the genus Blautia when compared with those with normal muscle mass (P=0.009). Logistic regression analysis revealed that the association between the genus Blautia and skeletal muscle mass remained significant even after adjusting for multiple confounding factors (P=0.012). Additionally, an increase in the genus Blautia was positively associated with excessive alcohol consumption (≥ 20 g/day, β=0.125, P=0.002) and negatively associated with regular yogurt intake (≥ 1 time/week, β=-0.101, P=0.010), independent of other lifestyle and dietary factors. Conclusion: Elevated levels of the genus Blautia were associated with reduced skeletal muscle mass in older Japanese adults, suggesting that improving the gut microbiota may be a potential approach to preserving muscle mass among this population.