New diagnostic criteria for sarcopenia

Sarcopenia is the main factor behind frailty, disability, and loss of independence. Falls are its most obvious consequence: in Australia, they remain the leading cause of hospitalizations and deaths from injuries. In 2024–2025, 253,800 hospitalizations were associated with falls; a year earlier, 6,722 people died after falling, and the damage to the healthcare system was estimated at $5.4 billion.

Primary care in Australia is already being directed to address the problem. Earlier this year, a proposed algorithm for screening, assessing, and treating poor muscle health in primary care was published. However, as the authors emphasize, this raises the question: when an elderly person says they have become weaker and slower, what exactly is the doctor looking for and what are they treating?

For decades, muscle was considered the answer. In the new study, the focus has already shifted away from muscle mass — now sarcopenia is determined by grip strength, gait speed, and getting up from a chair, because these indicators are much more accurate predictors of falls, disability, and death. However, the explanation has not changed, as both research and clinical practice still describe sarcopenia as a muscle disease, and interpret weakness as a consequence of muscle mass loss.

The data contradict this. Muscle mass loss explains only a modest portion of the age‑related decline in strength. Two people with the same muscle volume can have very different levels of strength and mobility. Huge resources have been invested in developing drugs and protein‑based strategies that reliably build muscle, yet the increase in what a person can actually do is disappointing. Physical exercise, by contrast, improves the strength and mobility of older adults even when muscle mass remains unchanged according to measurements.

The authors see a problem with the model. Aging not only reduces muscle mass — it degrades the entire motor system: everything involved in generating movement, from the brain and spinal cord through nerves and their connections to the muscle itself. Movements are planned more slowly, signals are transmitted less reliably and reach weaker, and the sense of balance and body position weakens. The muscle may still be present, but less command reaches it. An example is the task of getting up from a chair: this is a test of speed and power, not muscle mass, and power declines with age earlier and faster than muscle mass — it largely depends on how well the nerves recruit and activate muscle fibers.

The authors propose understanding sarcopenia as a disease of the aging motor system and formulate a five‑point agenda for international working groups that develop diagnostic criteria. For primary care physicians, the shift concerns what to pay attention to. The strength and speed of gait should be maintained in the arsenal, but in addition, it is important to assess how quickly a person gets up from a chair, not just whether they can do it, to notice instability during prolonged effort, to observe hand dexterity, and to note how walking changes during conversation.

A more thorough examination is needed when the weakness is asymmetric, develops quickly, or is disproportionate to the volume of lost muscle. Sedative and anticholinergic medications suppress motor regulation, so reviewing medications should be done in parallel with strength training, not after it.

The authors are honest about the limitations, as no one has yet shown that these measures are superior to existing screenings in terms of outcomes or cost, and expertise in neuromuscular medicine is unevenly distributed across primary care. What matters to them is something else — investments in validating practical tests that doctors can actually use, clinical guidelines with a step‑by‑step approach, and studies that measure the condition of nerves, not just muscles.

Rethinking sarcopenia as a disease of the motor system can lead to a better understanding of why a particular person is becoming weaker, to more targeted treatment, and to more effective strategies for preserving mobility and independence as the population ages. At the same time, it can redirect research and investment in healthcare from approaches focused on building muscle mass to multi‑component interventions that directly improve strength, movement, and daily functions.