Low muscle quality index (MQI) is an independent predictor of lower lung functioning measures in patients who are severely ill with post-COVID-19 syndrome, according to study findings published in BMC Pulmonary Medicine.
Low MQI has been previously linked with metabolic syndrome, metabolic markers, and the prediction of cardiovascular disease risk factors, but to date its association with pulmonary function is undefined. Therefore, investigators in Mexico sought to assess the association between MQI (defined as handgrip strength [HGS] divided by body mass index [BMI]; ie, MQI=HGS/BMI) and lung function in patients who were severely ill with post-COVID-19 syndrome.
The investigators conducted a cross-sectional study at the Instituto Nacional de Enfermedades Respiratorias in Mexico City from June 2020 through May 2023. The study included 748 outpatients (mean [SD] age, 54.62 [0.44] years) who had previously been hospitalized with moderate to severe COVID-19 confirmed by polymerase chain reaction (PCR) testing. Patients studied (36% women; mean [SD] BMI, 30.39 [6.21]kg/m2) had been hospitalized during the acute phase of the disease with blood oxygen saturation no greater than 93% and the arterial partial pressure of oxygen/fraction of inspired oxygen ratio less than 300 (PaO2/FiO2<300).
Patients were evaluated for the current study 3 months post-discharge. Participants were stratified by MQI as high-MQI (above the 50th percentile) and low-MQI (equal to or below the 50th percentile). Patients in the low-MQI group vs the high-MQI group tended to be older (58 vs 51 years) with a higher prevalence of obesity (54% vs 35%) and hypertension (43% vs 32%).
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The MQI could function as an indicator that determines the requirement for muscle training within pulmonary rehabilitation programs.
Additionally, in the low-MQI group vs the high-MQI group, invasive mechanical ventilation (IMV) had been more prevalent (72% vs 52%) and of greater duration (18 vs 15 days), and patients had experienced longer hospital stay (21 vs 14 days). Overall, 62% of participants had required mechanical ventilation and the median hospital stay had been 17 days.
Patients in the low-MQI group vs the high-MQI group had lower forced expiratory volume in 1 second (FEV1) in liters and percentage as well as lower mechanical function (forced vital capacity [FVC] in liters and percentage, lower FEV1/FVC ratio, and lower diffusing capacity of the lungs for carbon monoxide [DLCO]).
The relationship between mechanical respiratory function and low-MQI was significant in multivariate analysis adjusted for IMV, ischemic cardiopathy, hypertension, diabetes, and age. Neither unadjusted or adjusted models showed a significant difference in DLCO.
Study limitations include the use of a cross-sectional study design that could not determine causality and lack of data on lung function and muscle quality in participants prior to COVID-19 infection.
“The low-MQI serves as an independent predictor linked to pulmonary function parameters among individuals experiencing post-COVID-19 syndrome,” the investigators concluded. “The MQI could function as an indicator that determines the requirement for muscle training within pulmonary rehabilitation programs,” the study authors added.
