Purpose: The muscle quality index (MQI) was proposed as a measure to quantify age-related alterations in muscle function. It is unknown if the MQI predicts mortality.
Methods: This was a population-based cohort study from the Third National Health and Nutrition Survey (NHANES III; 1988-1994). The MQI was quantified using a timed sit-to-stand test, body mass, and leg length. Vital status was obtained through the National Center for Health Statistics. We fit multivariable-adjusted regression models to estimate the hazard ratio (HR) and 95% confidence interval (CI) between the MQI and mortality.
Results: During 14.6 years of follow-up, 3299 (73.1%) of 4510 study participants died. Lower MQI was associated with a higher risk of mortality (Ptrend <.001). The multivariable-adjusted HR for mortality was 1.50 (95% CI, 1.15-1.96) for those in the lowest quintile of MQI compared to the highest quintile. The association between MQI and mortality was stronger among males (highest vs. lowest quintile of MQI, HR = 1.37 [95% CI, 1.00-1.87]; Ptrend = .001) compared to females (highest vs. lowest quintile of MQI, HR = 1.27 (95% CI, 0.89-1.83); Ptrend = .044; Pinteraction = .005].
Conclusions: The MQI predicts mortality and may differ between males and females. Additional research examining the MQI is warranted.
Keywords: Aging; Mobility; Muscle strength; Physical activity; Physical function.
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