Impact of Daily Physical Activity as Measured by Commonly Available Wearables on Mealtime Glucose Control in Type 1 Diabetes

Abstract

Objective: In contrast with exercise, or structured physical activity (PA), glycemic disturbances due to daily unstructured PA in patients with type 1 diabetes (T1D) is largely underresearched, with limited information on treatment recommendations. We present results from retrospective analysis of data collected under patients' free-living conditions that illuminate the association between PA, as measured by an off-the-shelf activity tracker, and postprandial blood glucose control. Research Design and Methods: Data from 37 patients with T1D during two clinical studies with identical data collection protocols were analyzed retrospectively: 4 weeks of continuous glucose monitoring, carbohydrate intake, insulin injections, and PA (assessed through wearable activity tracker) were collected in free-living conditions. Five-hour glucose area under curves (GAUCs) following the last-bolused meal of every day were computed to assess postprandial glucose excursions, and their relation with corresponding antecedent PA was analyzed using linear mixed-effects regression models, accounting for meal, insulin, and current glycemic state. Results: Datasets yielded 845 days of data from 37 subjects (22.8 ± 11.6 days/subject); postmeal GAUC was negatively associated with total daily PA measured by step count (P = 0.025), and total time spent performing higher than light-intensity PA (P = 0.042). Patients with higher median total daily PA exhibited lower average postprandial GAUC (P < 0.01). Additional analyses indicated that daily PA likely presents an immediate and delayed impact on glucose control. Conclusion: Daily PA assessed by commonly available sensors is significantly associated with glycemic exposure after an evening meal, indicating that quantitative assessment of PA may be useful in mealtime treatment decisions.

Keywords: Activity tracker; Exercise; Physical activity; Postprandial glucose control; Step count; Type 1 diabetes.

Conflict of interest statement

No competing financial interests exist.

Figures

FIG. 1.

Example clinical translation of the results for a representative patient with body weight of 80.5 kg and TDI of 42.3 U. Correspondence between carbohydrates (CHO), insulin units, and PA with similar absolute contribution to the GAUC. Left panel: PA explored as total steps taken in the previous 12 h, right panel: PA explored as moderate- to high-intensity PA (expressed with higher-intensity PA) defined based on Fitbit activity levels. GAUC, glucose area under curve; PA, physical activity; TDI, total daily insulin.

FIG. 2.

Bar plot representation of the observed magnitude of decrease in the postprandial GAUC with an increment in the LN (total number of steps taken) for each hour preceding the mealtime (e.g., [0–1]: the hour right before the meal). These results are obtained from 12 separate LME models. LME, linear mixed-effects.