RESUMEN
OBJECTIVE: Digital behavior change interventions (DBCIs) are feasibly effective tools for addressing physical activity. However, in-depth understanding of participants' long-term engagement with DBCIs remains sparse. Since the effectiveness of DBCIs to impact behavior change depends, in part, upon participant engagement, there is a need to better understand engagement as a dynamic process in response to an individual's ever-changing biological, psychological, social, and environmental context. METHODS: The year-long micro-randomized trial (MRT) HeartSteps II provides an unprecedented opportunity to investigate DBCI engagement among ethnically diverse participants. We combined data streams from wearable sensors (Fitbit Versa, i.e., walking behavior), the HeartSteps II app (i.e. page views), and ecological momentary assessments (EMAs, i.e. perceived intrinsic and extrinsic motivation) to build the idiographic models. A system identification approach and a fluid analogy model were used to conduct autoregressive with exogenous input (ARX) analyses that tested hypothesized relationships between these variables inspired by Self-Determination Theory (SDT) with DBCI engagement through time. RESULTS: Data from 11 HeartSteps II participants was used to test aspects of the hypothesized SDT dynamic model. The average age was 46.33 (SD=7.4) years, and the average steps per day at baseline was 5,507 steps (SD=6,239). The hypothesized 5-input SDT-inspired ARX model for app engagement resulted in a 31.75 % weighted RMSEA (31.50 % on validation and 31.91 % on estimation), indicating that the model predicted app page views almost 32 % better relative to the mean of the data. Among Hispanic/Latino participants, the average overall model fit across inventories of the SDT fluid analogy was 34.22 % (SD=10.53) compared to 22.39 % (SD=6.36) among non-Hispanic/Latino Whites, a difference of 11.83 %. Across individuals, the number of daily notification prompts received by the participant was positively associated with increased app page views. The weekend/weekday indicator and perceived daily busyness were also found to be key predictors of the number of daily application page views. CONCLUSIONS: This novel approach has significant implications for both personalized and adaptive DBCIs by identifying factors that foster or undermine engagement in an individual's respective context. Once identified, these factors can be tailored to promote engagement and support sustained behavior change over time.
RESUMEN
BACKGROUND: Despite the health benefits, cancer survivors tend to exercise less after diagnosis and treatment. Wearable activity trackers (WATs) can provide avenues for self-monitoring and may enhance exercise motivation and enjoyment. However, less is known about the relationship between how often survivors use wearables and their amount of moderate to vigorous physical activity (MVPA). METHODS: Data was utilized from the National Cancer Institute's Health Information National Trend Survey 5 Cycles 3-4 (January 2019 - June 2020). To account for overdispersion and excessive zeros in the outcome variable (weekly minutes of MVPA), a zero inflated negative binomial regression model was used. RESULTS: The majority of the sample (n = 1369) were female (n = 735, 53.7 %), non-Hispanic White (n = 961, 70.2 %) and 34.3 % (n = 664) were between the ages of 65-74 years. Non-melanoma skin cancer was the most frequently reported cancer type (n = 334, 24.4 %) and 48.5 % (n = 664) reported that it had been 11 + years since their diagnosis. Survivors who reported daily WAT use were estimated to have 3.53 times higher number of MVPA minutes per week compared to survivors who reported non-daily WAT usage (RR: 3.53, 2.76-4.53, p = <0.001). Based on the model, daily WAT users had an expected mean MVPA of 202 min per week (95 % CI: 191.15-226.59) compared to non-daily users (132 min, 95 % CI: 119.81-140.22) and non-WAT users (88 min, 95 % CI: 84.46-92.50). CONCLUSION: According to this model, survivors who reported daily WAT use were estimated on average to have weekly MVPA minutes that meet or exceed MVPA recommendations (>= 150 min of MVPA per week) compared to survivors who reported infrequent or no WAT use. Wearables may provide an opportunity for survivors to engage in self-monitoring and can potentially support exercise tracking and engagement.