Background <p>Age-related decline in skeletal muscle mass among middle-aged and older adults is a major global public health concern and a critical factor affecting glucose metabolism. This study aims to investigate the association between the skeletal muscle mass index (SMI) and glycemic progression and remission in the middle-aged and older Chinese population with prediabetes.</p> Methods <p>We conducted a nationwide prospective cohort study among Chinese adults aged ≥ 45&#xa0;years. Individuals with prediabetes and their glucose outcomes were defined according to the American Diabetes Association criteria. Cox regression models and restricted cubic spline regression models were applied to evaluate the association between SMI and the progression or remission of individuals with prediabetes.</p> Results <p>A total of 2,591 participants with prediabetes at baseline (mean age: 60&#xa0;years) were included. After a median follow-up of 4&#xa0;years, 399 individuals (15.4%) progressed to diabetes, while 584 (22.5%) experienced remission to normoglycemia. Multivariable Cox regression analysis showed that SMI was linearly negatively associated with the progression to diabetes and linearly positively associated with glycemic remission in the prediabetic population. Furthermore, subgroup analyses revealed a significant interaction between education level and glycemic remission in individuals with prediabetes: among individuals with similar SMI levels, higher educational attainment was associated with an increased probability of normoglycemia reversion compared to lower educational attainment.</p> Conclusion <p>This nationwide cohort study among middle-aged and older Chinese adults demonstrates that SMI is associated with both the progression and remission of glycemic status in individuals with prediabetes: higher SMI levels are correlated with a reduced risk of diabetes progression and an increased likelihood of remission to normoglycemia.</p>