Understanding the development of healthy lifestyle behaviors as well as its early predictors and associated outcomes is paramount, given the importance of healthy lifestyle behaviors in academic success, health, and well-being. In this dissertation, I conducted two studies to investigate the development of three modifiable lifestyle behaviors (i.e., physical activity, sedentary behavior, and sleep duration) in middle childhood, using a nationally representative sample of US children from the Early Childhood Longitudinal Study, Kindergarten Class of 2010-11. Study 1 was designed to unpack the developmental associations among the three lifestyle behaviors by examining the transactional within-person associations and co-development. Moderate-to-vigorous physical activity (MVPA), video game use (as a measure of mentally active sedentary behavior), and sleep duration were reported by parents in 3rd through 5th grades. Results from the random intercept cross-lagged panel model showed that MVPA, video game use, and sleep duration were not transactionally related over time at the within-person level. Analysis with the multivariate latent growth curve model showed that changes in these lifestyle behaviors over time were not correlated either. These main findings were replicated across social contexts of socioeconomic status, gender, and race/ethnicity groups. Study 2 focused on investigating predictors and outcomes associated with developmental trajectories of the three lifestyle behaviors. Specifically, kindergarten self-regulation (rated by teachers) that reflects individual agency was examined as a predictor. Fifth grade externalizing and internalizing problems (rated by teachers), body mass index (assessed with weight and height), and academic achievement (assessed by reading, math, and science achievement) were included as mental health, physical health, and academic outcomes, respectively. Results showed that kindergarten self-regulation predicted initial levels (i.e., 3rd grade) of video game use and sleep duration. After controlling for the stability and other lifestyle behaviors, 5th grade externalizing problems and academic achievement were predicted by initial levels of sleep duration, and body mass index was predicted by initial levels of sleep duration and MVPA and changes in MVPA. Most of these findings were replicated in subsamples across social contexts. Overall, this dissertation provides important insight into the development of healthy lifestyle behaviors in US children.

The purpose of this thesis project was to examine the trajectories of physical activity among newly-diagnosed Obstructive Sleep Apnea (OSA) patients within the UC+WS group of the SleepWell24 study across the first 60 days of CPAP use, alone and based on Apnea-Hypopnea Index (AHI), Body Mass Index (BMI), sex, and age. The study utilizes objective data from the SleepWell24 randomized controlled trial conducted by a collaborative research team at Arizona State University and Mayo Clinic Arizona and Rochester. Participants use wearable sensors to track activity behaviors, such as sleep, sedentary behavior, light-intensity physical activity (LPA), and moderate-vigorous physical activity (MVPA). The primary aim of the study was to examine the physical activity trajectories among newly-diagnosed OSA patients over the first 8 weeks of CPAP use, utilizing the physical activity data from wearable sensors. The secondary aim was to assess the trajectories of physical activity between categories of AHI, BMI, sex, and age. Multilevel modeling was used to account for clustering within participants considering between and within subject variations, and week was used as a level 1 predictor in the model for LPA, and MVPA, and total activity (sum of LPA and MVPA), while between subject factors of BMI, sex, age, and AHI were also included in the model. It was found that there were no statistically significant trajectories of LPA, MVPA or total activity over the first 8 weeks of CPAP use within the sample of 30 participants. However, a few notable differences in physical activity were seen between categories of age, sex, and BMI. Also, there was a significant interaction found between BMI and each week that influenced the trajectory of physical activity within obese patients, as compared to participants considered overweight or with a lower BMI. Ultimately, this study provides insight into patterns of physical activity seen in a clinical population of OSA patients over the initial period of CPAP use.

Tools that accurately assess physical activity and sedentary behaviors have broad implications relative to understanding the association of adverse health outcomes and these behaviors. Given the ease of distribution and inexpensive nature of self-report tools, they are the most widely used means to assess human behavior in large-scale populations. The purpose of this study was to validate the ACT24 online self-report recall for measures of sedentary and active behavior against criterion measure. Participants of a larger study were asked to complete the ACT24 recall on a random day in three different weeks during which they were wearing the criterion device. A total of 16 recalls were completed that were used to assess ACT24 measures of sedentary, active, and MVPA behavior. Four different comparisons afforded this analysis: criterion sitting time to ACT24 sedentary time, criterion standing time to ACT24 active behavior, criterion stepping time to ACT24 active behavior, and criterion stepping of 3.0+METs to ACT24 MVPA. Results for the comparisons made between ACT24 sedentary time versus criterion sitting time and ACT24 active time to criterion active time showed little systematic differences at the group level, but the limits of agreement were relatively wide. The comparisons made between ACT24 active time to criterion stepping time and ACT24 MVPA to criterion stepping time at 3.0+ METs both showed a positive systematic difference. Increased incidence of physical activity was correlated with more difference between the measures, likely due to an underestimation of criterion active time measurement. These results are important in the preliminary validity analysis of ACT24 measures of active and sedentary time. Future directions include implementing validation protocols in larger and more diverse samples.