A flexible framework for synthesizing human activity patterns with application to sequential categorical data

The ability to synthesize realistic data in a parametrizable way is valuable for a number of reasons, including privacy, missing data imputation, and evaluating the performance of statistical and computational methods. When the underlying data generating process is complex, data synthesis requires approaches that balance realism and simplicity. In this paper, we address the problem of synthesizing sequential categorical data of the type that is increasingly available from mobile applications and sensors that record participant status continuously over the course of multiple days and weeks. We propose the paired Markov Chain (paired-MC) method, a flexible framework that produces sequences that closely mimic real data while providing a straightforward mechanism for modifying characteristics of the synthesized sequences. We demonstrate the paired-MC method on two datasets, one reflecting daily human activity patterns collected via a smartphone application, and one encoding the intensities of physical activity measured by wearable accelerometers. In both settings, sequences synthesized by paired-MC better capture key characteristics of the real data than alternative approaches

Development and validation of a screening instrument to assess the types and quality of foods served at home meals

<p>Abstract</p> <p>Background</p> <p>Although there is growing interest in assessing the home food environment, no easy-to-use, low cost tools exist to assess the foods served at home meals, making it difficult to assess the meal component of the food environment. The aim of this study was to develop and validate a user-friendly screener to assess the types of foods served at home meals.</p> <p>Methods</p> <p>Primary food preparing adults (n = 51) participated in a validation study in their own homes. Staff and participants independently completed a screener as participants cooked dinner. The screener assessed the types of foods offered, method(s) of preparation, and use of added fats. Two scale scores were created: 1) to assess offerings of foods in five food groups (meat and other protein, milk, vegetables, fruit, grains), 2) to assess the relative healthfulness of foods based on types offered, preparation method, and added fats. Criterion validity was assessed comparing staff and participant reports of individual foods (kappa (k)) and scale scores (Spearman correlations).</p> <p>Results</p> <p>Criterion validity was high between participants' and staffs' record of whether major food categories (meat and other protein, bread and cereal, salad, vegetables, fruits, dessert) were served (k = 0.79-1.0), moderate for reports of other starches (e.g., rice) being served (k = 0.52), and high for the Five Food Group and Healthfulness scale scores (r = 0.75-0.85, <it>p </it>< .001).</p> <p>Conclusions</p> <p>This new meal screening tool has high validity and can be used to assess the types of foods served at home meals allowing a more comprehensive assessment of the home food environment.</p

School lunch and snacking patterns among high school students: Associations with school food environment and policies

OBJECTIVES: This study examined associations between high school students' lunch patterns and vending machine purchases and the school food environment and policies. METHODS: A randomly selected sample of 1088 high school students from 20 schools completed surveys about their lunch practices and vending machine purchases. School food policies were assessed by principal and food director surveys. The number of vending machines and their hours of operation were assessed by trained research staff. RESULTS: Students at schools with open campus policies during lunchtime were significantly more likely to eat lunch at a fast food restaurant than students at schools with closed campus policies (0.7 days/week vs. 0.2 days/week, p < .001). Student snack food purchases at school were significantly associated with the number of snack machines at schools (p < .001) and policies about the types of food that can be sold. In schools with policies, students reported making snack food purchases an average of 0.5 ± 1.1 days/week as compared to an average of 0.9 ± 1.3 days/week in schools without policies (p < .001). In schools in which soft drink machines were turned off during lunch time, students purchased soft drinks from vending machines 1.4 ± 1.6 days/week as compared to 1.9 ± 1.8 days/week in schools in which soft drink machines were turned on during lunch (p = .040). CONCLUSION: School food policies that decrease access to foods high in fats and sugars are associated with less frequent purchase of these items in school among high school students. Schools should examine their food-related policies and decrease access to foods that are low in nutrients and high in fats and sugars

Familial correlates of adolescent girls' physical activity, television use, dietary intake, weight, and body composition

<p>Abstract</p> <p>Background</p> <p>The family environment offers several opportunities through which to improve adolescents' weight and weight-related behaviors. This study aims to examine the cross-sectional relationships between multiple factors in the family environment and physical activity (PA), television use (TV), soft drink intake, fruit and vegetable (FV) intake, body mass index (BMI), and body composition among a sample of sociodemographically-diverse adolescent girls.</p> <p>Methods</p> <p>Subjects included girls (mean age = 15.7), 71% of whom identified as a racial/ethnic minority, and one of their parents (dyad n = 253). Parents completed surveys assessing factors in the family environment including familial support for adolescents' PA, healthful dietary intake, and limiting TV use; parental modeling of behavior; and resources in the home such as availability of healthful food. Girls' PA and TV use were measured by 3-Day Physical Activity Recall (3DPAR) and dietary intake by survey measures. BMI was measured by study staff, and body fat by dual-energy X-ray absorptiometry (DXA). Hierarchical linear regression models tested individual and mutually-adjusted relationships between family environment factors and girls' outcomes.</p> <p>Results</p> <p>In the individual models, positive associations were observed between family support for PA and girls' total PA (p = .011) and moderate-to-vigorous PA (p=.016), home food availability and girls' soft drink (p < .001) and FV (p < .001) intake, and family meal frequency and girls' FV intake (p = .023). Across the individual and mutually-adjusted models, parental modeling of PA, TV, and soft drink and FV intake was consistently associated with girls' behavior.</p> <p>Conclusions</p> <p>Helping parents improve their physical activity and dietary intake, as well as reduce time watching television, may be an effective way to promote healthful behaviors and weight among adolescent girls.</p

The validation of a home food inventory

<p>Abstract</p> <p>Background</p> <p>Home food inventories provide an efficient method for assessing home food availability; however, few are validated. The present study's aim was to develop and validate a home food inventory that is easily completed by research participants in their homes and includes a comprehensive range of both healthful and less healthful foods that are associated with obesity.</p> <p>Methods</p> <p>A home food inventory (HFI) was developed and tested with two samples. Sample 1 included 51 adult participants and six trained research staff who independently completed the HFI in participants' homes. Sample 2 included 342 families in which parents completed the HFI and the Diet History Questionnaire (DHQ) and students completed three 24-hour dietary recall interviews. HFI items assessed 13 major food categories as well as two categories assessing ready-access to foods in the kitchen and the refrigerator. An obesogenic household food availability score was also created. To assess criterion validity, participants' and research staffs' assessment of home food availability were compared (staff = gold standard). Criterion validity was evaluated with kappa, sensitivity, and specificity. Construct validity was assessed with correlations of five HFI major food category scores with servings of the same foods and associated nutrients from the DHQ and dietary recalls.</p> <p>Results</p> <p>Kappa statistics for all 13 major food categories and the two ready-access categories ranged from 0.61 to 0.83, indicating substantial agreement. Sensitivity ranged from 0.69 to 0.89, and specificity ranged from 0.86 to 0.95. Spearman correlations between staff and participant major food category scores ranged from 0.71 to 0.97. Correlations between the HFI scores and food group servings and nutrients on the DHQ (parents) were all significant (p < .05) while about half of associations between the HFI and dietary recall interviews (adolescents) were significant (p < .05). The obesogenic home food availability score was significantly associated (p < .05) with energy intake of both parents and adolescents.</p> <p>Conclusion</p> <p>This new home food inventory is valid, participant-friendly, and may be useful for community-based behavioral nutrition and obesity prevention research. The inventory builds on previous measures by including a wide range of healthful and less healthful foods rather than foods targeted for a specific intervention.</p

Increasing weight-bearing physical activity and calcium-rich foods to promote bone mass gains among 9–11 year old girls: outcomes of the Cal-Girls study

BACKGROUND: A two-year, community-based, group-randomized trial to promote bone mass gains among 9–11 year-old girls through increased intake of calcium-rich foods and weight-bearing physical activity was evaluated. METHODS: Following baseline data collection, 30 5th-grade Girl Scout troops were randomized to a two-year behavioral intervention program or to a no-treatment control group. Evaluations were conducted at baseline, one year, and two years. Measures included bone mineral content, density, and area (measured by DXA), dietary calcium intake (24-hour recall), and weight-bearing physical activity (physical activity checklist interview). Mixed-model regression was used to evaluate treatment-related changes in bone mineral content (g) for the total body, lumbar spine (L1-L4), proximal femur, one-third distal radius, and femoral neck. Changes in eating and physical activity behavioral outcomes were examined. RESULTS: Although the intervention was implemented with high fidelity, no significant intervention effects were observed for total bone mineral content or any specific bone sites. Significant intervention effects were observed for increases in dietary calcium. No significant intervention effects were observed for increases in weight-bearing physical activity. CONCLUSION: Future research needs to identify the optimal dosage of weight-bearing physical activity and calcium-rich dietary behavior change required to maximize bone mass gains in pre-adolescent and adolescent girls

Associations of American Indian Children\u27s Screen-Time Behavior With Parental Television Behavior, Parental Perceptions of Children\u27s Screen Time, and Media-Related Resources in the Home

Introduction: American Indian children have high rates of overweight and obesity, which may be partially attributable to screen-time behavior. Young children\u27s screen-time behavior is strongly influenced by their environment and their parents\u27 behavior. We explored whether parental television watching time, parental perceptions of children\u27s screen time, and media-related resources in the home are related to scree time (ie, television, DVD/video, video game, and computer use) among Oglala Lakota youth residing on or near the Pine Ridge Reservation in South Dakota. Methods: We collected baseline data from 431 child and parent/caregiver pairs who participated in Bright Start, a group-randomized, controlled, school-based obesity prevention trial to reduce excess weight gain. Controlling for demographic characteristics, we used linear regression analysis to assess associations between children\u27s screen time and parental television watching time, parental perceptions of children\u27s screen time, and availability of media-related household resources. Results: The most parsimonious model for explaining children screen time included the children\u27s sex, parental body mass index, parental television watching time, how often the child watched television after school or in the evening, parental perception that the child spent too much time playing video games, how often the parent limited the child\u27s television time, and the presence of a VCR/DVD player or video game player in the home (F7,367 = 14.67; P \u3c .001; adjusted R2 = .37). The presence of a television in the bedroom did not contribute significantly to the model. Conclusion: Changes in parental television watching time, parental influence over children\u27s screen-time behavior, and availability of media-related resources in the home could decrease screen time and may be used as a strategy for reducing overweight and obesity in American Indian children