Although less muscle mass is associated with greater diabetes prevalence in cross-sectional studies, prospective data in middle-aged Black and White adults are lacking. Middle age is a critical window as accelerated muscle loss is yet to occur, and preventing diabetes reduces lifelong morbidity and mortality. We hypothesized that lower appendicular lean mass adjusted for body mass index (ALM/BMI) is associated with higher incident diabetes in middle-aged Black and White adults in the Coronary Artery Risk Development in Young Adults (CARDIA) study. ALM/BMI was measured by dual x-ray energy absorptiometry (DXA) in 2005-06 among middle-aged US men (n=855) and women (n=1045) in CARDIA. Incident diabetes occurred if any of the following were met in 2010-11 or 2015-16 among persons without diabetes in 2005-06: fasting glucose ≥7 mmol/L (126 mg/dL), 2-hour glucose ≥11.1 mmol/L (200 mg/dL) on a 75-gram glucose tolerance test, HbA
1C
≥48 mmol/mol (6.5%), or use of glucose-lowering medications. We used logistic regression models with sex stratification given sex differences in ALM. In men, mean age was 45.0 ± 3.5 y, BMI 28.0 ± 4.3 kg/m
2
, and ALM/BMI 1.07 ± 0.14 m
2
. In women, mean age was 45.2 ± 3.6 years, BMI 28.4 ± 6.4 kg/m
2
, and ALM/BMI 0.73 ± 0.12 m
2
. Diabetes developed in 70 men (8.2%) and 72 women (6.9%). For each standard deviation increase in ALM/BMI (m
2
), the risk of diabetes decreased by 22% in men and 29% in women (Table 1). After adjusting for age, race, smoking, education, physical activity, and waist circumference, the association of ALM/BMI with diabetes incidence was no longer significant. Associations were similar between race-ethnic groups. In conclusion, less relative skeletal muscle mass is associated with a greater risk of developing diabetes in middle-aged men and women over 10 years, which is largely explained by the relationship of ALM/BMI to other metabolic risk factors. Low skeletal muscle mass in middle age is a marker for greater diabetes risk and may be a target for preventative interventions.
Gender-Specific Associations between Low Skeletal Muscle Mass and Albuminuria in the Middle-Aged and Elderly Population
