JMIR Publications

ABSTRACT

Background:

Diabetic foot ulcers (DFUs) are a life-changing complication of diabetes. There is increasing evidence that plantar temperature monitoring can reduce the incidence and recurrence of DFUs. Once daily foot temperature monitoring is the current guideline for identifying early signs of foot inflammation and DFUs. However, single readings of physiological signals are known to increase the risk of misdiagnosis when there are fluctuations of the signal throughout the day.

Objective:

The purpose of this study was to evaluate whether intra-day temperature asymmetry signals were stable or varied as a function of time in individuals at risk of DFU.

Methods:

Sixty-four participants with diabetes (mean age = 68 ± 13.8 years) were provided with multi-modal sensory insoles (Orpyx® Sensory Insoles) to monitor continuous temperature data at five plantar locations with a frequency of once/minute during a 90-day study window. 1,080 data days, 5400 contralateral temperature asymmetry signals, were included. The Augmented Dickey-Fuller test was used to determine whether the temperature asymmetry signals were stationary (stable) or non-stationary (time-varying).

Results:

The majority (82%) of temperature asymmetry signals were time-varying, with intra-day fluctuations potentially driven by physiological and environmental factors. Nearly half (44%) of time-varying signals included a mix of concerning (>2.2°C) and non-concerning (≤2.2°C) measurements, indicating the limitations of single measurements in reliably identifying DFU risk. Statistical analysis revealed significant variability in stable versus time-varying patterns both within and across participants. Notably, days with time-varying signals and concerning asymmetry measurements showed dispersion of concerning periods across participants, time windows and days, rather than consistent daily patterns.

Conclusions:

Continuous monitoring could provide deeper insights into plantar temperature dynamics, uncovering associations with individual-specific factors such as vascular status, historical ulcer locations, activity, gait, and foot anatomy. These findings support the need for personalized monitoring protocols and leveraging continuous data to better inform clinical decision-making.