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Essay 06 · Writing · The Missing Ledger series

From snapshot to signal

A position paper on remote patient monitoring as the functional half of measuring muscle — and why it is not a fall alarm

one reading → a continuous signal

The question I am asked most often about remote patient monitoring is how to fit it into a preventative-imaging story, and the honest answer is that most people wire it in through the wrong door. They reach for frailty and falls, because that is the intuitive clinical hook and the one a funder understands. I understand the temptation, but I think it is a mistake to lead there. Remote monitoring earns its place not as a fall alarm but as the functional, longitudinal half of measuring muscle — the half a scan cannot capture. Imaging tells you the structure of the muscle on one day. Monitoring tells you what that muscle can still do, every day after. You need both, and I will argue that owning the first is precisely what makes the second defensible.

Two halves of the same measurement

Sarcopenia was never defined as low muscle mass alone. The European consensus made low muscle strength the primary criterion and grades severity by physical performance[S1]; the 2024 Global Leadership Initiative went further and treated physical performance as an outcome of the disease, the thing we are ultimately trying to protect[S2]. So a body-composition CT — the muscle area and muscle quality read off a single L3 slice — measures one axis of the disease with real precision, and is silent on the other. Function is not a footnote to mass; it is half the definition, and it is the half that moves.

Gait speed is the cleanest example, and it is not a soft measure. In a pooled analysis of nine cohorts and 34,485 older adults, walking speed predicted survival across its entire range — a hazard ratio of 0.88 for every 0.1 m/s faster — and did so about as well as a model built from age, sex, chronic conditions, smoking, blood pressure and hospitalisations combined[S20]. One number, measured at the pace someone walks down a corridor, carries as much prognostic weight as a page of history. The point for anyone building in this space is simple: the functional half of muscle is measurable, it is powerful, and — unlike a scan — it changes week to week, which is exactly why it wants to be monitored rather than snapshotted.

Why frailty and falls is the endpoint, not the entrance

None of this is an argument against caring about falls. Falls and the fractures that follow them are the endpoint the whole exercise is trying to prevent, and they are what make the case fundable. My caution is narrower and, I think, commercial: if remote monitoring enters as fall detection, it lands in the pendant-alarm market — a crowded, low-margin category that reacts to an event after it has happened. Measuring declining gait speed, cadence, daily activity and sit-to-stand — the digital biomarkers of frailty — is a different and more valuable thing, because it sees the decline coming and can be acted on before someone is on the floor. Wearables can already capture these markers unsupervised, in the patient's own home, well enough to classify frailty risk[S21], and in a sicker population pendant sensors distinguished those who would and would not tolerate chemotherapy as early as day six of a cycle[S22]. Falls are the consequence to protect against. Function is the thing to measure. Lead with the measurement and falls fall out of it; lead with the alarm and you have built a commodity.

It closes the loop that imaging leaves open

The strongest reason to bring monitoring in is that it finishes a sentence imaging can only start. Opportunistic imaging identifies the person with low muscle who did not know it. The treatment — progressive resistance exercise and adequate protein — is the same evidence-based core it always is. But the scan that raised the flag cannot tell you whether the programme is working; the next one is a year away. Remote monitoring is what sits in that year. It tells you whether gait speed and daily activity are actually rising, whether the patient is doing the training, and whether to escalate or reassure — a continuous read on the intervention rather than an annual verdict on it.

This is sharpest in the population everyone is now watching: patients losing weight on GLP-1 and dual-agonist therapies, a meaningful share of which is lean mass rather than fat[S11]. A bathroom scale rewards them for the loss and tells them nothing about the muscle going with it. A falling gait speed or a quietly dropping step count would — and in an older, frailer patient that signal matters more than the number on the scale ever will. Imaging can benchmark the muscle before and after; monitoring is what catches the trouble in between.

The economics I keep coming back to

There is a business argument here that is consistent with everything I have written about value in radiology. A scan is paid for once and valued by the decision it changes. Remote monitoring converts that single diagnostic transaction into a longitudinal relationship — recurring, low-marginal-cost information about the same patient over time, anchored to an imaging baseline nobody else holds. That is not a new revenue trick; it is the same value-based logic extended along the time axis. The organisation that owns the structural baseline and the functional signal has something a wearable company selling step counts, and a radiology practice selling single studies, each only half of.

The counter-case, which I hold at the same time

I am sceptical of monitoring technology by default, and the burden of proof sits with outcomes, not novelty. Consumer-grade wearable accuracy for gait and frailty in older adults is variable, and much of the strongest data comes from research-grade sensors under supervision rather than the watch a patient actually owns[S21]. Adherence in the frail and elderly — the people who most need it — is the hardest to sustain and the least studied. The evidence that monitoring changes hard outcomes, rather than producing a prettier dashboard, is still thin. And there is a data-governance question that is not optional: continuous physiological data from someone's home is sensitive, it needs a clear custody and consent model, and reimbursement for remote monitoring in Australia remains its own unresolved argument. A signal nobody is funded to act on, or trusted to hold, is not a service.

What I argue for

Bring remote monitoring in as the functional, longitudinal complement to the imaging baseline — not as a fall alarm, and not as a gadget in search of a use. Measure function continuously against a structural read taken once; use validated devices with the accuracy stated honestly; govern the data as carefully as we govern the images; and hold the whole thing to the same standard I hold everything else in this series — that it changes a decision or an outcome, and can be audited against one. Framed that way, frailty and falls stop being the way in and become what the system is quietly built to prevent. That is the version of remote monitoring I would put my name to, and it is the one that fits the ledger.

References

Literature identified via PubMed and web search, July 2026. DOIs to be re-verified before publication.

Dr Lisa Sorger is a consultant radiologist, healthcare executive, medical administrator, company director and founder of myradiologist.ai. She writes on the economics and ethics of preventative imaging and diagnostic radiology. Every claim in this paper is sourced to the public record.

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All views expressed here are my own personal opinions and are not medical advice. General information only — not clinical or financial advice. myradiologist.ai · ABN 29 692 758 115 · ACN 692 758 115