Daily steps and healthcare costs: Osaka study of 20,950 adults

Associate Professor Haruka Kato of the Graduate School of Human Life and Ecology at Osaka Metropolitan University analyzed how daily step counts relate to later healthcare expenditures, EurekAlert reports. The dataset combined objective step counts from "A-Smile", the official mobile health app of Osaka Prefecture, with administrative health insurance claims. It covered 20,950 long-term app users aged 40 and over, a total of 338,706 person-months from 2020 to 2023. eurekalert.org

The results were published in SSM - Population Health. Earlier studies of physical activity and healthcare costs mostly relied on self-reported questionnaires and linear models, so the actual shape of the relationship and its change across the lifespan remained largely unclear. Kato used generalized additive models, which estimate flexible curves instead of assuming straight lines. The authors note that the model describes associations, not causal effects. eurekalert.org

Age dependence of the step–cost relationship

The model output is a three-dimensional surface of predicted costs across age and daily steps. For middle-aged adults aged 40–64 the surface was nearly flat, and the costs of this group appeared to be driven by factors other than walking. eurekalert.org

Among adults aged 65 and over, predicted costs peaked in the low-step region and dropped sharply as step counts rose. In other words, the gradient linking steps to healthcare costs steepens markedly with age. eurekalert.org

Plateau near 11,000 steps

One feature was the same in both age groups: predicted costs stopped declining and leveled off at around 11,000 steps a day. The plateau began at 11,317 steps for middle-aged adults and at 10,612 steps for older adults. The slope changes with age, but the location of the plateau does not. eurekalert.org

"Our findings suggest that promoting walking among older adults could substantially contribute to reducing healthcare expenditures because predicted costs are far more sensitive to daily steps in this group," Kato said. She added that, since costs are modeled as a flexible function of age and steps, the expected reduction can be estimated for any given increase in steps at any age. eurekalert.org

To illustrate this, Kato released an interactive version of the fitted model. It shows the predicted expenditure and its confidence interval for any combination of age and daily steps within the range of the study. eurekalert.org

Osaka Metropolitan University: predicted healthcare costs level off near 11,000 daily steps

Age dependence of the step–cost relationship

Plateau near 11,000 steps

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