Percent Vital Capacity as a Predictor of Sarcopenia in Non-obese Non-smoking Middle-aged Females

<p> [Purpose] It is known that the loss of muscle mass as the characteristic of sarcopenia cannot be simply evaluated based on a decrease in the body mass index (BMI). This study was performed to determine whether a decrease in the percent vital capacity (%VC), which indicates a decrease in the respiratory muscle mass, can be used as a predictor of sarcopenia in non-obese non-smoking middle-aged females.</p><p> [Methods] The subjects consisted of 280 non-smoking females aged 40-44 years who underwent respiratory function tests in our institution between April 2012 and March 2017. The exclusion criteria were height <145 cm and forced expiratory volume in one second percentage <70. The subjects were classified according to the BMI quartile into groups Q1-Q4, and %VC was compared among the 4 groups. In addition, to obtain %VC estimated from BMI, the mean BMI and %VC in each of 8 BMI segments (S1-S8 in ascending order) were calculated.</p><p> [Results] The mean %VC was significantly lower in the low BMI groups (group Q1, 93.81 ± 12.19) than in the average BMI group (group Q2, 98.60 ± 10.14; group Q3, 100.37 ± 11.50) (Q3 vs. Q1: p = 0.0014; Q2 vs. Q1: p = 0.013), but did not differ between the high (group Q4, 98.53 ± 8.86) and average groups (Q3 vs. Q4: p = 0.29). Graphical representation of %VC estimated from BMI revealed an accelerated decrease in %VC with a reduction in BMI in the underweight females, but a gentle decrease in %VC with a reduction in BMI in the overweight females.</p><p> [Discussion] Since the forced expiratory volume reflects the muscle mass of the entire body, there is a possibility that a decrease in %VC reflects "a state of decreased muscle mass and strength" as the pre-sarcopenia stage. When a decrease in %VC is observed in non-obese middle-aged females, appropriate nutritional guidance and muscle strength training may be necessary.</p><p> [Conclusion] This study suggested that a decrease in %VC in non-obese non-smoking middle-aged females may be a predictor of sarcopenia.</p>