The research team, led by Takuya Nishino of the Department of Health Policy and Management at Nippon Medical School, designed the study around a methodological device known as landmark analysis. Instead of asking a single question about the entire hospital stay, the investigators froze time at two specific points, hospital day 3 and hospital day 7, and examined what had changed in each patient up to those moments. They then tracked whether the patient experienced a first documented in-hospital fall within the following 30 days. This design matters because fall risk is not static. A patient who walks in with intact mobility and normal blood values may, by the end of the first week, be a very different physiological creature than the one who was admitted, and a risk score calculated at the front door cannot see that transformation.

The scale of the dataset gives the conclusions unusual weight. Of 112,103 eligible patients aged 65 years or older, 83,297 remained in the day-3 cohort and 61,071 in the day-7 cohort after the researchers applied their inclusion criteria. Patients ranged in age from 65 to 106 years, and roughly 40 percent of each cohort was female. Because the study drew on electronic health records and administrative data from two tertiary centers, the population reflects the everyday complexity of acute hospital medicine, with all its comorbidities, medications, and incomplete documentation. Missing data, an unavoidable feature of real-world records, were handled with multiple imputation by chained equations, a statistical technique that fills gaps by modeling each incomplete variable conditionally on the others, and the results held up across sensitivity analyses designed to probe the robustness of the associations.

The functional signal centered on transfer ability, the capacity to move between a bed, a chair, and a standing position, which is one of the most fundamental building blocks of independence. The researchers classified each patient’s functional trajectory by comparing transfer status at admission with transfer status at the landmark day. What they found was strikingly consistent: patients whose transfer impairment persisted or worsened by hospital day 3 faced a higher risk of falling in the subsequent month, and the same held true at day 7. Acute functional decline, meaning a deterioration between admission and the landmark, was associated with elevated fall risk at day 7 but not at day 3. That asymmetry is itself informative. It suggests that the earliest days of a stay may not capture decline that has not yet had time to emerge, while a full week of observation reveals patients on a downward functional slope who are precisely the ones most likely to fall.

The physiological signals were equally specific. Declines in hemoglobin, the oxygen-carrying pigment of red blood cells, were independently associated with higher fall risk at both landmarks, and so were drops in serum sodium, the principal electrolyte governing the tonicity of extracellular fluid. Changes in serum albumin, a protein often used as a marker of nutritional status and inflammation, showed no independent association with falls. The selectivity is important. It indicates that the relationship is not a generic marker of being sick, but something closer to a mechanistic story about how the body maintains the conditions required for safe movement.

Both of the implicated parameters have plausible biological routes to the floor. Anemia reduces oxygen delivery to muscles and the brain, and prior research has linked low hemoglobin to declines in physical performance and to dynapenia, the age-related loss of muscle strength. A patient whose hemoglobin falls during hospitalization, whether through blood loss, hemodilution from intravenous fluids, or underlying illness, may experience fatigue, weakness, and orthostatic lightheadedness, each of which undermines the delicate neuromuscular coordination that transfers and walking demand. Hyponatremia has an even more direct neurological pedigree. Sodium is essential for the electrochemical signaling of neurons, and even mild chronic hyponatremia has been associated in earlier studies with unsteadiness, attention deficits, gait disturbance, and increased rates of falls and fractures. A falling sodium level in an older inpatient may therefore quietly erode the cognitive and motor precision that prevents a misstep, long before anyone notices a problem.

Why albumin failed to make the cut is a question the authors address through the lens of prior literature. Serum albumin is a notoriously slippery indicator, influenced by inflammation, hydration, liver function, and capillary leakage as much as by nutrition, and its trajectory during a short hospital stay may simply move too slowly or too noisily to track the fast-changing physiology that precedes a fall. Hemoglobin and sodium, by contrast, can shift meaningfully within days in response to bleeding, fluid shifts, diuretics, and the stress response of acute illness. In that sense, the study’s negative finding for albumin is as useful as its positive ones, because it tells clinicians which laboratory trends are worth scheduling repeated checks for and which are not, at least for the specific purpose of fall prediction.

The practical implications reach into one of the most stubborn problems in hospital safety. Fall prevention programs have proliferated for decades, yet systematic reviews and meta-analyses, including work cited by the authors, show that their effects are often modest, and that most conventional risk assessment tools are completed once, at admission, and then filed away. The new study argues for a rhythm rather than a snapshot: scheduled reassessment of transfer ability and targeted laboratory parameters on hospital days 3 and 7, complementing the admission evaluation. Such a rhythm would catch evolving vulnerability, the patient who was low-risk on arrival but is becoming high-risk as anemia deepens or sodium drifts down, and it would give nursing staff a time-sensitive trigger to intensify interventions, whether that means closer supervision during transfers, bed and chair alarms, mobility assistance, or a medication review. The authors frame this as a way to identify older patients who require intensified fall-prevention measures, and the landmark structure of their analysis maps almost directly onto a feasible clinical workflow.

The study’s limitations are the familiar ones of retrospective design. The researchers could observe associations, not prove causation, and unmeasured factors, from sedating medications to delirium to staffing levels on a given ward, may shape both the laboratory trajectories and the fall events. Falls documented in administrative data may also undercount the true total, since not every fall is recorded. The data came from two Japanese tertiary hospitals, and the datasets, which contain sensitive individual-level clinical information, are not publicly available, which limits independent replication, although the multicenter design and the sheer sample size lend credibility to the central patterns. The work was supported by the Japan Society for the Promotion of Science through a KAKENHI grant, and the team included specialists spanning health policy, cardiovascular medicine, medical safety, nursing, and anesthesiology, a breadth that reflects the multidisciplinary nature of the problem itself.

What makes the study resonate beyond geriatrics is its conceptual shift. Falls have long been treated as a geriatric syndrome, a multifactorial failure at the intersection of aging bodies and hazardous environments, and the field’s own literature acknowledges that hospitalization itself is a driver of disability, a phenomenon memorably described in the medical literature as patients who were probably able to ambulate but whose capacity quietly evaporated during a stay. By showing that the seeds of a fall are visible in measurable trajectories within the first week, the Japanese team offers a way to intervene before the fall rather than after it. The message for hospitals is deceptively simple: check the blood, check the transfer, and check again on day 3 and day 7. The message for science is broader still, that the most dangerous changes in aging patients may be the ones that unfold slowly, in routine laboratory values and bedside observations, waiting for someone to look twice.

Subject of Research: Early in-hospital functional and physiological changes as predictors of fall risk in hospitalized older adults

Article Title: Association between early in-hospital physiological and functional changes and fall risk in older adults: a retrospective multicenter cohort study

Article References: Nishino, T., Kubota, Y., Miyagi, Y., Tanabe, N., Yamaguchi, F., Ito, H., Soh, S., Yano, A., Mizuno, M., Kim, C., Ishii, Y., & Asai, K. (2026). Association between early in-hospital physiological and functional changes and fall risk in older adults: a retrospective multicenter cohort study. European Geriatric Medicine. https://doi.org/10.1007/s41999-026-01622-8

Image Credits: AI Generated

DOI: 10.1007/s41999-026-01622-8

Keywords: falls, older adults, hospitalization, functional decline, hemoglobin, hyponatremia, serum albumin, landmark analysis, geriatrics, patient safety, cohort study, fall prevention