Usability of Healthmine app

Assessed via the System Usability Scale (SUS), a 10-item questionnaire measuring perceived usability of a system or technology. Each item is rated on a 5-point Likert scale ranging from 1 ("strongly disagree") to 5 ("strongly agree"). The total SUS score is calculated by summing the score contributions from each item (for odd-numbered items, subtract 1 from the user response; for even-numbered items, subtract the user response from 5), multiplying the sum by 2.5, resulting in a score ranging from 0 to 100. Higher scores indicate better perceived usability, with scores above 68 considered above average usability.

15 days and 30 days after starting study-provided CGM and Healthmine app use

Days with CGM data

The number of days with continuous glucose monitoring data available will be divided by the total number of requested days of wear (30) to obtain percentage of days with data.

30-day CGM wear period

Days with Fitbit data

The number of days with Fitbit data available will be divided by the total number of requested days of wear (30) to obtain percentage of days with data.

30-day Fitbit wear period

Mean CGM glucose

Mean glucose obtained from study-provided CGM

30-day CGM wear period

Step count

Step count data will be obtained via study-provided Fitbit.

30-day Fitbit wear period

Diabetes Self-Management

Assessed via the Diabetes Self-Management Questionnaire (DSMQ), a 16-item self-report questionnaire measuring diabetes self-care activities associated with glycemic control. Each item is rated on a 4-point Likert scale (0 = "does not apply to me" to 3 = "applies to me very much"). Items are summed (after reverse-coding negatively worded items) and transformed to a 0-10 scale, where higher scores indicate better self-management.

Baseline and 30 days (change from baseline to 30 days)

Treatment Self-Regulation

Assessed via the Treatment Self-Regulation Questionnaire (TSRQ), a questionnaire measuring the degree to which a person's motivation for health behaviors is relatively autonomous (self-determined) versus controlled (motivated by external factors). Items are rated on a 7-point Likert scale (1 = "not at all true" to 7 = "very true"). The TSRQ yields subscale scores for autonomous regulation, controlled regulation, and amotivation, with higher scores on each subscale indicating greater levels of that type of motivation.

Baseline and 30 days (change from baseline to 30 days)

Self-Reported Physical Activity

Assessed via the PACE+ Physical Activity Measure, a brief self-report questionnaire measuring physical activity levels. Participants report the number of days per week they engage in moderate or vigorous physical activity for at least 30 minutes (or 60 minutes for adolescents). The measure yields separate scores for moderate and vigorous activity (each ranging from 0-7 days per week), with higher scores indicating greater physical activity frequency.

Baseline and 30 days (change from baseline to 30 days)

Diet Quality

Assessed via the Prime Diet Quality Score (PDQS), a food-based dietary assessment tool that evaluates diet quality across 15 food group components. The PDQS includes 10 adequacy components (dark green leafy vegetables, cruciferous vegetables, carrots, other vegetables, citrus fruits, other fruits, fish/seafood, eggs, whole grains, and low-fat dairy) and 5 moderation components (red meat as main dish, processed meat, refined grains and baked goods, sugar-sweetened beverages, and fried foods). Each component is scored based on consumption frequency, with higher scores indicating greater intake of health-promoting foods and lower intake of foods that should be consumed in moderation. The total PDQS ranges from 0-30, with higher scores indicating better overall diet quality.

Baseline and 30 days (change from baseline to 30 days)

Glucose monitoring satisfaction

Assessed via the Glucose Monitoring Satisfaction Survey (GMSS) for Type 2 Diabetes, a 15-item questionnaire measuring patient satisfaction with their glucose monitoring device. Items are rated on a 5-point Likert scale (1 = "strongly disagree" to 5 = "strongly agree"). The GMSS yields four subscale scores: Openness (items 1, 8, 10, 14), Emotional Burden (items 2, 5, 9, 13), Behavioral Burden (items 3, 6, 11, 15), and Worthwhileness (items 4, 7 \[reverse coded\], 12). Subscale scores are calculated as the mean of item responses, with higher scores indicating greater openness, greater burden (for burden subscales), and greater worthwhileness, respectively. A total satisfaction score is calculated as the mean of all items after reverse-coding items 2, 3, 5, 6, 7, 9, 11, 13, and 15, with higher total scores indicating greater overall satisfaction with glucose monitoring.

30 days (following CGM wear period)

Glucose coefficient of variation

Based on CGM glucoses, coefficient of variation will be calculated by dividing the standard deviation of glucose readings by the mean glucose level, then multiplying by 100 to get a percentage.

30-day CGM wear period

Glucose time below range

Percent of time with CGM glucose less than 70 mg/dL

30-day CGM wear period

Glucose time in range

Percent of time with CGM glucose 70-180 mg/dL

30-day CGM wear period

Glucose time above range

Percent of time with CGM glucose above 180 mg/dL

30-day CGM wear period

Mean amplitude of glycemic excursions

A measure of glucose variability calculated from CGM data, calculated by dividing the standard deviation of glucose readings by the mean glucose level, then multiplying by 100 to get a percentage.

30-day CGM wear period