Bayesian isotonic regression and trend analysis

1 SUMMARY. In many applications, the mean of a response variable can be assumed to be a non-decreasing function of a continuous predictor, controlling for covariates. In such cases, interest often focuses on estimating the regression function, while also assessing evidence of an association. This article proposes a new framework for Bayesian isotonic regression and order restricted inference based on a constrained piecewise linear model with unknown knot locations, corresponding to thresholds in the regression function. The non-decreasing constraint is incorporated through a prior distribution consisting of a product mixture of point masses (accounting for flat regions) and truncated autoregressive normal densities. An MCMC algorithm is used to obtain a smooth estimate of the regression function and posterior probabilities of an association for different regions of the predictor. Generalizations to categorical outcomes and multiple predictors are described, and the approach is applied to data from a study of pesticide exposure and birth weight

Bayesian Latent Factor Regression for Functional and Longitudinal Data

In studies involving functional data, it is commonly of interest to model the impact of predictors on the distribution of the curves, allowing flexible e ects on not only the mean curve but also the distribution about the mean. Characterizing the curve for each subject as a linear combination of a high-dimensional set of potential basis functions, we place a sparse latent factor regression model on the basis coe cients. We induce basis selection by choosing a shrinkage prior that allows many of the loadings to be close to zero. The number of latent factors is treated as unknown through a highly-e cient, adaptive-blocked Gibbs sampler. Predictors are included on the latent variables level, while allowing different predictors to impact different latent factors. This model induces a framework for functional response regression in which the distribution of the curves is allowed to change flexibly with predictors. The performance is assessed through simulation studies and the methods are applied to data on blood pressure trajectories during pregnancy

Development of a Health Survey Instrument for 5- to 8-Year-Old Youths

Measuring program outcomes is required for documenting effectiveness of interventions with youths participating in programs funded through the U.S. Department of Agriculture\u27s Children, Youth, and Families at Risk (CYFAR) initiative. The California CYFAR program provided programming for youths aged 5–8, which necessitated the development of an age-appropriate survey measure. Evaluating younger youths to assess healthful living outcomes is challenging, especially with youths in kindergarten through second grade. This article addresses development and testing of the measure and resultant lessons learned. Recommendations for developing an evaluation survey for younger youths are provided

Characteristics associated with US Walk to School programs

Participation in Walk to School (WTS) programs has grown substantially in the US since its inception; however, no attempt has been made to systematically describe program use or factors associated with implementation of environment/policy changes

Reliability and validity of a nutrition and physical activity environmental self-assessment for child care

<p>Abstract</p> <p>Background</p> <p>Few assessment instruments have examined the nutrition and physical activity environments in child care, and none are self-administered. Given the emerging focus on child care settings as a target for intervention, a valid and reliable measure of the nutrition and physical activity environment is needed.</p> <p>Methods</p> <p>To measure inter-rater reliability, 59 child care center directors and 109 staff completed the self-assessment concurrently, but independently. Three weeks later, a repeat self-assessment was completed by a sub-sample of 38 directors to assess test-retest reliability. To assess criterion validity, a researcher-administered environmental assessment was conducted at 69 centers and was compared to a self-assessment completed by the director. A weighted kappa test statistic and percent agreement were calculated to assess agreement for each question on the self-assessment.</p> <p>Results</p> <p>For inter-rater reliability, kappa statistics ranged from 0.20 to 1.00 across all questions. Test-retest reliability of the self-assessment yielded kappa statistics that ranged from 0.07 to 1.00. The inter-quartile kappa statistic ranges for inter-rater and test-retest reliability were 0.45 to 0.63 and 0.27 to 0.45, respectively. When percent agreement was calculated, questions ranged from 52.6% to 100% for inter-rater reliability and 34.3% to 100% for test-retest reliability. Kappa statistics for validity ranged from -0.01 to 0.79, with an inter-quartile range of 0.08 to 0.34. Percent agreement for validity ranged from 12.9% to 93.7%.</p> <p>Conclusion</p> <p>This study provides estimates of criterion validity, inter-rater reliability and test-retest reliability for an environmental nutrition and physical activity self-assessment instrument for child care. Results indicate that the self-assessment is a stable and reasonably accurate instrument for use with child care interventions. We therefore recommend the Nutrition and Physical Activity Self-Assessment for Child Care (NAP SACC) instrument to researchers and practitioners interested in conducting healthy weight intervention in child care. However, a more robust, less subjective measure would be more appropriate for researchers seeking an outcome measure to assess intervention impact.</p

Validity and Reliability of a School Travel Survey

Despite the growing interest in active (ie, nonmotorized) travel to and from school, few studies have explored the measurement properties to assess active travel. We evaluated the criterion validity and test–retest reliability of a questionnaire with a sample of young schoolchildren to assess travel to and from school, including mode, travel companion, and destination after school

Characteristics Associated with US Walk to School Programs: A cross-sectional study

Abstract Participation in Walk to School (WTS) programs has grown substantially in the US since its inception; however, no attempt has been made to systematically describe program use or factors associated with implementation of environment/policy changes. Objective Describe the characteristics of schools' WTS programs by level of implementation. Methods Representatives from 450 schools from 42 states completed a survey about their WTS program's infrastructure and activities, and perceived impact on walking to school. Level of implementation was determined from a single question to which respondents reported participation in WTS Day only (low), WTS Day and additional programs (medium), or making policy/environmental change (high). Results The final model showed number of community groups involved was positively associated with higher level of implementation (OR = 1.78, 95%CI = 1.44, 2.18), as was funding (OR = 1.56, 95%CI = 1.26, 1.92), years of participation (OR = 1.44, 95% CI = 1.23, 1.70), and use of a walkability assessment (OR = 3.22, 95%CI = 1.84, 5.64). Implementation level was modestly associated with increased walking (r = 0.18). Conclusion Strong community involvement, some funding, repeat participation, and environmental audits are associated with progms that adopt environmental/policy change, and seem to facilitate walking to school

Menus in Child Care: A Comparison of State Regulations with National Standards

The purpose of this project was to compare individual state regulations regarding menus for child-care centers and family child-care homes with national menu standards. For all 50 states and the District of Columbia, state regulations were compared with menu standards found in Caring for Our Children—National Health and Safety Performance Standards: Guidelines for Out-of-Home Child Care Programs. Specifically, these guidelines suggest that (a) menus must be posted or made available to parents, (b) menus must be dated, (c) menus must reflect food served, (d) menus must be planned in advance, and (e) menus must be kept on file. One additional standard, that menus in child care are reviewed by a nutrition professional, was added to this review. Data were collected between June and August of 2007. Substantial variation existed among state regulations regarding menus. For child-care centers, seven states (14%) included regulations on all five standards, and 13 states (25%) had regulations on four of the five menu standards. Ten states (20%) did not have any regulations on the five menu standards. For family child-care homes, only three states (6%) had regulations on all five menu standards; four states (8%) had regulations on four of the five menu standards. Twenty-seven states (53%) did not have any regulations on the five standards for menus. Within the same state, regulations for child-care centers and family child-care homes often did not match. Overall, great discrepancies were found between model child-care menu policies and current state regulations in most states. States have the opportunity to improve regulations regarding menus to ensure that child-care providers develop accurate, specific, and healthful menus

Characterizing weekly self-reported antihypertensive medication nonadherence across repeated occasions

BackgroundLittle is known about weekly variability in medication nonadherence both between and within persons.PurposeTo characterize medication nonadherence across repeated, closely spaced occasions.MethodsThis prospective cohort study comprised four unannounced telephone assessment occasions, each separated by approximately 2 weeks. On each occasion, adult outpatients taking at least a single antihypertensive medication completed a measure of extent of, and reasons for, nonadherence.ResultsTwo hundred and sixty-one participants completed 871 (83%) of 1,044 occasions. Nonadherence was reported on 152 (17.5%) of 871 occasions by 93 (36%) of 261 participants. The most commonly endorsed reasons for nonadherence were forgetting (39.5%), being busy (23.7%), and traveling (19.7%). Among 219 participants completing at least three occasions, 50% of the variability in extent of nonadherence was a result of within-person fluctuations, and 50% was a result of between-person differences.ConclusionInterventions to reduce nonadherence should be informed by variability in the extent of nonadherence and specific reasons for nonadherence