Association of Cut-Point Free Metrics and Common Clinical Tests Among Older Adults After Proximal Femoral Fracture

TL;DR

This study shows that MX metrics, a new way to measure physical activity intensity, are useful in tracking recovery from hip fractures in older adults.

Contribution

The study introduces MX metrics as a cut-point free method for assessing physical activity in older adults recovering from proximal femoral fractures.

Findings

MX metrics (M1–M30) showed strong correlations with mobility capacity and perception in later recovery stages of PFF.

Older adults in acute recovery had lower physical activity intensity compared to those in later recovery groups.

Shorter-duration MX metrics were more discriminative in differentiating recovery groups.

Abstract

What are the main findings?
Clinical lower limb assessments (both subjective and objective) were more discriminative in differentiating between the four PFF recovery groups in older adults.Older adults in the acute proximal femoral fracture recovery group demonstrated lower physical activity intensity compared to those in later recovery groups, with the differences being more pronounced for shorter-duration MX metrics (M1–M5).

Clinical lower limb assessments (both subjective and objective) were more discriminative in differentiating between the four PFF recovery groups in older adults.

Older adults in the acute proximal femoral fracture recovery group demonstrated lower physical activity intensity compared to those in later recovery groups, with the differences being more pronounced for shorter-duration MX metrics (M1–M5).

What is the implication of the main finding?
The cut-point free method (e.g., MX metrics) is useful for measuring the physical activity magnitude of older adults recovering from proximal femoral fractures. Higher lower limb capacity and perception outcomes were strongly correlated with greater daily activity intensity, particularly in older adults at later stages of proximal femoral fracture recovery.

The cut-point free method (e.g., MX metrics) is useful for measuring the physical activity magnitude of older adults recovering from proximal femoral fractures.

Higher lower limb capacity and perception outcomes were strongly correlated with greater daily activity intensity, particularly in older adults at later stages of proximal femoral fracture recovery.

Wearable and lightweight devices facilitate real-world physical activity (PA) assessments. MX metrics, as a cut-point-free parameter, evaluate acceleration above which the most active X minutes are accumulated. It provides insights into the intensity of PA over specific durations. This study evaluated the association of MX metrics and clinical tests in older adults recovering from proximal femoral fracture (PFF). Analyses were conducted on the PFF cohort from the baseline assessment of the Mobilise-D project using an accelerometer-based device. Participants (N = 396) were categorized into four recovery groups: acute, post-acute, extended recovery, and long-term recovery. Mobility capacity was assessed through the 6 min walking test (6MinWT), Short Physical Performance Battery (SPPB), 4-m walking test (4MWT), and hand grip (HG) strength. Mobility perception was evaluated using the Late-Life Function and Disability Instrument (LLFDI). Eight MX metrics (M1–M90) were calculated using the GGIR package in R. Results showed a moderate to strong positive correlation between M1 and M30 and lower limb mobility capacity tests and mobility perception (Lower Extremity domains) particularly in the extended and long-term recovery groups. MX metrics can be used for measuring PA intensity among older adults recovering from PFF. Hence, MX metrics have a high potential for clinical use as personalized PA targets in PFF rehabilitation.

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