JMIR Publications

ABSTRACT

Background:

Algorithms estimating real-world digital mobility outcomes (DMOs) are increasingly validated in healthy adults and various disease cohorts. However, their accuracy and reliability in older adults after hip fractures, who often walk slowly for short durations, is underexplored.

Objective:

The objective of this study was to examine DMO accuracy and reliability in a hip fracture cohort, considering walking bout (WB) duration, physical function, days since surgery, and walking aid usage.

Methods:

Participants were monitored in their natural environment for 2.5 hours using a lower back single wearable device and a reference system combining inertial modules, distance sensors, and pressure insoles. DMO estimates from 164 WBs from 11 participants obtained from the single wearable device were assessed against the reference system on a WB and a participant level, including walking speed, cadence, stride length, stride duration, number of steps and walking distance. We stratified by WB duration (All WBs, WBs >10s, WBs 10-30s, WBs >30s), lower versus higher Short Physical Performance Battery (SPPB) scores, and observed whether days since surgery and walking aid usage affected DMO accuracy and reliability.

Results:

Walking speed, cadence, stride duration, number of steps, and distance stratified by WB duration showed Intraclass Correlation Coefficients (ICCs) ranging from 0.50-0.99, and mean relative errors (MREs) ranging from –6.9% to 12.8%. Stride length showed poor reliability with ICCs ranging from 0.30-0.49 and MREs from 6.1% to 13.2%. Walking speed and distance ICCs in the higher SPPB score group ranged from 0.85-0.99 and MREs from –10.1% to –1.7%. In the lower SPPB score group, walking speed and distance ICCs ranged from 0.17-0.99 and MREs from 13.5% to 32.6%. We did not observe a discernible effect of time since surgery or walking aid usage on walking speed or distance estimates.

Conclusions:

Five accurate and reliable real-world DMOs were identified in older adults after hip fractures: walking speed, cadence, stride duration, number of steps, and distance. Accuracy and reliability of most DMOs improved when excluding WBs <10 seconds and were higher in WBs >30 seconds compared to 10-30 seconds WBs and for those with higher physical function. DMOs can capture daily mobility as early as 1 month after surgery, also in people using walking aids. However, as most WBs in this cohort are of short duration, there is a trade-off between more accurate and reliable walking speed and distance estimates when excluding short-duration WBs, and the loss of a substantial amount of data. These results have important implications for future research aiming to establish clinical validity of DMOs, and enable clinicians to evaluate the effects of interventions on daily life mobility in detail, which in turn facilitates the design of optimal care pathways. Clinical Trial: ISRCTN – 12246987 https://doi.org/10.1186/ISRCTN12246987