Abstract Body (Do not enter title and authors here): Background
Obesity phenotypes are increasingly used to define cardiovascular diseases (CVD) risks. Age-related deteriorations in skeletal muscle function have ignited interest in the co-occurrence of sarcopenia and obesity in older adults. However, the traditional definition of sarcopenia (low appendicular skeletal mass [ASM] and handgrip strength [HGS]) may lead to underdiagnosis of sarcopenic obesity (SO) in overweight individuals (due to higher muscle mass). To address this enigma, we evaluated the use of muscle quality (MQ), as an alternative metric for SO, in association with cardiac function.
Methods
Community older adults without CVD were prospectively annotated for skeletal mass, HGS and cardiac function via bioimpedance analysis, dynamometer, and simultaneous acquisition of echocardiography respectively. Sarcopenia was defined by low ASM and low HGS. Low MQ (HGS divided by upper body ASM) was defined by males<5.76kg/kg and females<5.475kg/kg. Aerobic capacity (VO2 max,ml/kg/min) was computed by a physical activity prediction model. Mitral early diastolic inflow velocity to early diastolic annular tissue velocity (E/e’) and early to late diastolic inflow velocity (E/A) ratios were recorded.
Results
Overall, low MQ was prevalent (34.3%) in n=574 participants (59% females), but only 17.4% fulfilled sarcopenia diagnosis. Higher BMI correlated with higher ASM but lower MQ (Fig 1). Low MQ prevalence was higher in the obese compared to the non-obese (64.7% vs 30.2%, p<0.0001). Low MQ group was significantly older (69.0±10.4 vs 64.8±14.0 years, p<0.0001), had higher prevalence of dyslipidemia (49.2% vs 40.9% p=0.002) and hypertension (45.2% vs 39.3% p<0.0001) than the normal MQ group. The low MQ group had greater left ventricular mass (129±45 vs 114±44, grams, p<0.0001), left atrial volumes (37±14 vs 33±13, ml, p=0.001), and demonstrated a greater degree of diastolic dysfunction (lower E/A (0.89±0.28 vs 1.1±0.49, p<0.0001 and higher E/e’(8.63±2.42 vs 8.00±2.58, p=0.005), compared to the high MQ. VO2 max was lower in low MQ group (33±5.7 vs 36±6.7, p<0.0001). By regression, low MQ was associated with E/A (β=-0.119, adjusted p<0.0001) and VO2 max (β=-0.137, p<0.0001) (Table 1).
Conclusion
Muscle quality is a useful metric of muscle function for sarcopenia in obese older adults. The associations between low MQ with diastolic dysfunction and reduced aerobic capacity corroborate the clinical impact of MQ as a defining metric of sarcopenia in obesity.