Reference Values for Skeletal Muscle Mass - Current Concepts and Methodological Considerations

Area of Science:

• Gerontology
• Nutritional Science
• Biomedical Engineering

Background:

• Assessing low skeletal muscle mass (SM) is vital for diagnosing sarcopenia in aging and disease.
• Heterogeneous methods and terminologies create discrepancies in diagnostic criteria and consensus definitions.

Purpose of the Study:

• To analyze and summarize published cut-offs for SM used in clinical and research settings.
• To facilitate the comparison of SM results between different studies.

Main Methods:

• Systematic review of 64 studies identifying published reference values for SM parameters.
• Comparison of methodological assumptions and limitations, including SM normalization for body size and fat mass (FM).
• Evaluation of proxies for total SM, such as appendicular lean soft tissue by DXA or BIA, against whole-body imaging.

Main Results:

• Proxies like DXA and BIA show high correlation with whole-body imaging but have errors limiting individual assessment and change detection.
• Obesity's impact on muscle quality may lead to sarcopenia underestimation; normalizing SM for FM is suggested.
• Direct comparison of SM results requires identical methods, devices (BIA/DXA), and reference populations.

Conclusions:

• Standardized methods and appropriate reference populations are essential for comparing SM assessment results.
• Limitations of SM proxies and FM normalization must be considered in longitudinal studies, obese populations, and older subjects.