Abstract P432: Higher Muscle-to-Abdominal Cavity Ratio is Associated with Lower Odds of Type II Diabetes in Older Women
Authors: Larsen Britta , Allison Matthew , Kang Eugene , Saad Sarah , Laughlin Gail A , Araneta Maria R , Barrett-Connor Elizabeth , Wassel Christina L 
Published: July 2021

Background:
Excess abdominal adipose tissue has been identified as an important factor in the development of type II diabetes. Lean muscle tissue also plays an important role in glucose regulation, yet research on the role of muscle in diabetes etiology is limited. Abdominal muscle mass could be particularly relevant for normal weight diabetics, for whom excessive abdominal adipose tissue may play less of a role.

Objective:
To explore the association between muscle-to-abdominal cavity area ratio and prevalent diabetes in older community-dwelling women in the Rancho Bernardo Study, UCSD Filipino Women’s Health Study, and the Health Assessment Study of African-American Women.

Methods:
Participants were 421 women (40% Caucasian, 28% Filipina, 32% African American) with a mean age of 64 (6.9) years. Abdominal muscle and fat areas were measured using computed tomography (CT) scans, and were used to compute a muscle-to-abdominal cavity area ratio (MACR). Based on body mass index (BMI), participants were classified as normal weight (18-24.9 kg/m2), overweight (25-29.9), or obese (30+). Prevalent diabetes was defined as self-report of physician diagnosis, anti-diabetes medication use, fasting morning glucose ≥ 126 mg/dL or 2 hour glucose ≥ 200mg/dL. MACR was modeled per standard deviation (SD) and logistic regression was used to examine the association with diabetes while adjusting for relevant covariates.

Results:
Prevalent diabetes was seen in 12.8% of the sample (54 of 421). In age and race/ethnicity adjusted models, each SD increase in MACR was associated with significant reduced odds of diabetes (OR = 0.62, CI: 0.43-0.89, p = 0.01), which remained significant after further adjustment for BMI category, smoking, physical activity, hypertension, anti-hypertensive drugs, and estrogen use (OR = 0.64, CI: 0.41-0.98, p = .041). The association was modestly attenuated after further adjusting for visceral fat area (OR = 0.70, CI: 0.44-1.10, p = 0.12). Normal weight women with diabetes had significantly less total muscle (p = 0.045) and smaller MACR’s (p = 0.001) than those without diabetes, while this was not seen for overweight or obese women with diabetes. Stratified by BMI category, MACR was significantly associated with lower odds of diabetes for normal weight women across all three models (fully adjusted OR = 0.37, CI: 0.15-0.90, p =.03), yet was not associated with diabetes in any models for women who were overweight or obese (all p > 0.50). Interactions of MACR with race/ethnicity were not significant.

Conclusions:
Muscle-to-abdominal cavity ratio is associated with reduced likelihood of type II diabetes in women. This association differs by BMI category, with muscle showing the greatest protection in normal weight women, and no effect in overweight or obese women. This highlights the potential role of low muscle mass as a risk factor for diabetes, particularly in women who may appear to be at low risk.