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We propose a new Bayesian nonparametric method for estimating the causal effects of mediation in the presence of a post-treatment confounder. The methodology is motivated by the Rural Lifestyle Intervention Treatment Effectiveness Trial (Rural LITE) for which there is interest in estimating causal mediation effects but is complicated by the presence of a post-treatment confounder. We specify an enriched Dirichlet process mixture (EDPM) to model the joint distribution of the observed data (outcome, mediator, post-treatment confounder, treatment, and baseline confounders). For identifiability, we use the extended version of the standard sequential ignorability (SI) as introduced in Hong et al. along with a Gaussian copula model assumption. The observed data model and causal identification assumptions enable us to estimate and identify the causal effects of mediation, that is, the natural direct effects (NDE) and natural indirect effects (NIE). Our method enables easy computation of NIE and NDE for a subset of confounding variables and addresses missing data through data augmentation under the assumption of ignorable missingness. We conduct simulation studies to assess the performance of our proposed method. Furthermore, we apply this approach to evaluate the causal mediation effect in the Rural LITE trial, finding that there was not strong evidence for the potential mediator. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to develop a predictive algorithm of "high‐risk" periods for weight regain after weight loss. Methods: Longitudinal mixed‐effects models and random forest regression were used to select predictors and develop an algorithm to predict weight regain on a week‐to‐week basis, using weekly questionnaire and self‐monitoring data (including daily e‐scale data) collected over 40 weeks from 46 adults who lost ≥5% of baseline weight during an initial 12‐week intervention (Study 1). The algorithm was evaluated in 22 adults who completed the same Study 1 intervention but lost <5% of baseline weight and in 30 adults recruited for a separate 30‐week study (Study 2). Results: The final algorithm retained the frequency of self‐monitoring caloric intake and weight plus self‐report ratings of hunger and the importance of weight‐management goals compared with competing life demands. In the initial training data set, the algorithm predicted weight regain the following week with a sensitivity of 75.6% and a specificity of 45.8%; performance was similar (sensitivity: 81%–82%, specificity: 30%–33%) in testing data sets. Conclusions: Weight regain can be predicted on a proximal, week‐to‐week level. Future work should investigate the clinical utility of adaptive interventions for weight‐loss maintenance and develop more sophisticated predictive models of weight regain. [ABSTRACT FROM AUTHOR]

ContextObservational studies and polyp recurrence trials are not conclusive regarding the effects of a low-fat dietary pattern on risk of colorectal cancer, necessitating a primary prevention trial.ObjectiveTo evaluate the effects of a low-fat eating pattern on risk of colorectal cancer in postmenopausal women.Design, setting, and participantsThe Women's Health Initiative Dietary Modification Trial, a randomized controlled trial conducted in 48,835 postmenopausal women aged 50 to 79 years recruited between 1993 and 1998 from 40 clinical centers throughout the United States.InterventionsParticipants were randomly assigned to the dietary modification intervention (n = 19,541; 40%) or the comparison group (n = 29,294; 60%). The intensive behavioral modification program aimed to motivate and support reductions in dietary fat, to increase consumption of vegetables and fruits, and to increase grain servings by using group sessions, self-monitoring techniques, and other tailored and targeted strategies. Women in the comparison group continued their usual eating pattern.Main outcome measureInvasive colorectal cancer incidence.ResultsA total of 480 incident cases of invasive colorectal cancer occurred during a mean follow-up of 8.1 (SD, 1.7) years. Intervention group participants significantly reduced their percentage of energy from fat by 10.7% more than did the comparison group at 1 year, and this difference between groups was mostly maintained (8.1% at year 6). Statistically significant increases in vegetable, fruit, and grain servings were also made. Despite these dietary changes, there was no evidence that the intervention reduced the risk of invasive colorectal cancer during the follow-up period. There were 201 women with invasive colorectal cancer (0.13% per year) in the intervention group and 279 (0.12% per year) in the comparison group (hazard ratio, 1.08; 95% confidence interval, 0.90-1.29). Secondary analyses suggested potential interactions with baseline aspirin use and combined estrogen-progestin use status (P = .01 for each). Colorectal examination rates, although not protocol defined, were comparable between the intervention and comparison groups. Similar results were seen in analyses adjusting for adherence to the intervention.ConclusionIn this study, a low-fat dietary pattern intervention did not reduce the risk of colorectal cancer in postmenopausal women during 8.1 years of follow-up.Clinical trials registrationClinicalTrials.gov Identifier: NCT00000611.

ContextMultiple epidemiologic studies and some trials have linked diet with cardiovascular disease (CVD) prevention, but long-term intervention data are needed.ObjectiveTo test the hypothesis that a dietary intervention, intended to be low in fat and high in vegetables, fruits, and grains to reduce cancer, would reduce CVD risk.Design, setting, and participantsRandomized controlled trial of 48,835 postmenopausal women aged 50 to 79 years, of diverse backgrounds and ethnicities, who participated in the Women's Health Initiative Dietary Modification Trial. Women were randomly assigned to an intervention (19,541 [40%]) or comparison group (29,294 [60%]) in a free-living setting. Study enrollment occurred between 1993 and 1998 in 40 US clinical centers; mean follow-up in this analysis was 8.1 years.InterventionIntensive behavior modification in group and individual sessions designed to reduce total fat intake to 20% of calories and increase intakes of vegetables/fruits to 5 servings/d and grains to at least 6 servings/d. The comparison group received diet-related education materials.Main outcome measuresFatal and nonfatal coronary heart disease (CHD), fatal and nonfatal stroke, and CVD (composite of CHD and stroke).ResultsBy year 6, mean fat intake decreased by 8.2% of energy intake in the intervention vs the comparison group, with small decreases in saturated (2.9%), monounsaturated (3.3%), and polyunsaturated (1.5%) fat; increases occurred in intakes of vegetables/fruits (1.1 servings/d) and grains (0.5 serving/d). Low-density lipoprotein cholesterol levels, diastolic blood pressure, and factor VIIc levels were significantly reduced by 3.55 mg/dL, 0.31 mm Hg, and 4.29%, respectively; levels of high-density lipoprotein cholesterol, triglycerides, glucose, and insulin did not significantly differ in the intervention vs comparison groups. The numbers who developed CHD, stroke, and CVD (annualized incidence rates) were 1000 (0.63%), 434 (0.28%), and 1357 (0.86%) in the intervention and 1549 (0.65%), 642 (0.27%), and 2088 (0.88%) in the comparison group. The diet had no significant effects on incidence of CHD (hazard ratio [HR], 0.97; 95% confidence interval [CI], 0.90-1.06), stroke (HR, 1.02; 95% CI, 0.90-1.15), or CVD (HR, 0.98; 95% CI, 0.92-1.05). Excluding participants with baseline CVD (3.4%), the HRs (95% CIs) for CHD and stroke were 0.94 (0.86-1.02) and 1.02 (0.90-1.17), respectively. Trends toward greater reductions in CHD risk were observed in those with lower intakes of saturated fat or trans fat or higher intakes of vegetables/fruits.ConclusionsOver a mean of 8.1 years, a dietary intervention that reduced total fat intake and increased intakes of vegetables, fruits, and grains did not significantly reduce the risk of CHD, stroke, or CVD in postmenopausal women and achieved only modest effects on CVD risk factors, suggesting that more focused diet and lifestyle interventions may be needed to improve risk factors and reduce CVD risk.Clinical trials registrationClinicalTrials.gov Identifier: NCT00000611.

BackgroundThe role of walking, as compared with vigorous exercise, in the prevention of cardiovascular disease remains controversial. Data for women who are members of minority racial or ethnic groups are particularly sparse.MethodsWe prospectively examined the total physical-activity score, walking, vigorous exercise, and hours spent sitting as predictors of the incidence of coronary events and total cardiovascular events among 73,743 postmenopausal women 50 to 79 years of age in the Women's Health Initiative Observational Study. At base line, participants were free of diagnosed cardiovascular disease and cancer, and all participants completed detailed questionnaires about physical activity. We documented 345 newly diagnosed cases of coronary heart disease and 1551 total cardiovascular events.ResultsAn increasing physical-activity score had a strong, graded, inverse association with the risk of both coronary events and total cardiovascular events. There were similar findings among white women and black women. Women in increasing quintiles of energy expenditure measured in metabolic equivalents (the MET score) had age-adjusted relative risks of coronary events of 1.00, 0.73, 0.69, 0.68, and 0.47, respectively (P for trend,

Objective: The current study was a randomized controlled trial investigating the effect of an innovative, short-term lifestyle intervention on weight gain in female freshman college students. Participants: Ninety-five freshmen were recruited from a large public university in the United States. Methods: Participants completed baseline assessments and were randomized to a 5-session, 4-week intervention or wait-list control, with assessments at posttest and 3-month follow-up. Results: The hypothesized time by group interaction was not significant, p = 0.393; however, trends suggested that control participants maintained baseline weight, whereas intervention participants lost -2.07 kg by posttest but regained 1.05 kg at follow-up. Significantly more intervention participants (47.0%) decreased their daily caloric intake by = 200 kcal compared with control (31.7%), p = 0.050. Conclusion: Brief intervention to prevent weight gain was not effective in this sample. Future studies should investigate lengthening the intervention to enhance effectiveness and increasing recruitment to improve statistical power.

Objective: Although behavioral weight-loss interventions produce short-term weight loss, long-term maintenance remains elusive. This randomized trial examined whether learning a novel set of "stability skills" before losing weight improved long-term weight management. Stability skills were designed to optimize individuals' current satisfaction with lifestyle and self-regulatory habits while requiring the minimum effort and attention necessary. Method: Overweight/obese women (N = 267) were randomly assigned to one of two 6-month interventions and assessed at baseline and at 6, 12, and 18 months. Maintenance First women participated first in an 8-week stability skills maintenance module and then in a standard 20-week behavioral weight-loss program. Weight Loss First women participated first in a standard 20-week behavioral weight-loss program and then in a standard 8-week problem-solving skills maintenance module. There was no intervention staff contact during the 12-month follow-up period (6-18 months). Results: As designed, Maintenance First participants lost the same percentage of initial weight during the 6-month intervention period as Weight Loss First participants (M = -8.6%, SD = 5.7, vs. M = -9.1%, SD = 6.9; t = -0.6, p = 0.52). However, Maintenance First participants regained significantly less weight during the 12-month follow-up period (6-18 months) than Weight Loss First participants (M = 3.2 lb, SD = 10.4, vs. M = 7.3 lb, SD = 9.9 [M = 1.4 kg, SD = 4.7, vs. M = 3.3 kg, SD = 4.5]; t = 3.3, p = 0.001, d = 0.4). Conclusion: Learning stability skills before losing weight was successful in helping women to maintain weight loss without intervention staff contact during follow-up. These results can inform the study design of future innovative interventions. (Contains 1 figure and 2 tables.)

Purpose: Rural residents have higher rates of chronic diseases compared to their urban counterparts, and obesity may be a major contributor to this disparity. This study is the first analysis of obesity prevalence in rural and urban adults using body mass index classification with measured height and weight. In addition, demographic, diet, and physical activity correlates of obesity across rural and urban residence are examined. Methods: Analysis of body mass index (BMI), diet, and physical activity from 7,325 urban and 1,490 rural adults in the 2005-2008 National Health and Nutrition Examination Survey (NHANES). Findings: The obesity prevalence was 39.6% (SE = 1.5) among rural adults compared to 33.4% (SE = 1.1) among urban adults (P= 0.006). Prevalence of obesity remained significantly higher among rural compared to urban adults controlling for demographic, diet, and physical activity variables (odds ratio = 1.18, P= 0.03). Race/ethnicity and percent kcal from fat were significant correlates of obesity among both rural and urban adults. Being married was associated with obesity only among rural residents, whereas older age, less education, and being inactive was associated with obesity only among urban residents. Conclusions: Obesity is markedly higher among adults from rural versus urban areas of the United States, with estimates that are much higher than the rates suggested by studies with self-reported data. Obesity deserves greater attention in rural America. (Contains 4 tables.)

Purpose: To compare the costs of parent-only and family-based group interventions for childhood obesity delivered through Cooperative Extension Services in rural communities. Methods: Ninety-three overweight or obese children (aged 8 to 14 years) and their parent(s) participated in this randomized controlled trial, which included a 4-month intervention and 6-month follow-up. Families were randomized to either a behavioral family-based intervention (n = 33), a behavioral parent-only intervention (n = 34), or a waitlist control condition (n = 26). Only program costs data for the parent-only and family-based programs are reported here (n = 67). Assessments were completed at baseline, post-treatment (month 4) and follow-up (month 10). The primary outcome measures were total program costs and cost per child for the parent-only and family interventions. Findings: Twenty-six families in the parent-only intervention and 24 families in the family intervention completed all 3 assessments. As reported previously, both intervention programs led to significantly greater decreases in weight status relative to the control condition at month 10 follow-up. There was no significant difference in weight status change between the parent-only and family interventions. Total program costs for the parent-only and family interventions were $13,546 and $20,928, respectively. Total cost per child for the parent-only and family interventions were $521 and $872, respectively. Conclusions: Parent-only interventions may be a cost-effective alternative treatment for pediatric obesity, especially for families in medically underserved settings.

Summary: Background: General and eating disorder (ED) psychopathology are common among children and adults with overweight/obesity; few studies have examined their course of change throughout family‐based behavioural obesity treatment (FBT) and maintenance. Objectives: Examine: (1) the changes in the parent and child general and ED psychopathology during FBT and maintenance interventions; (2) the associations between change in psychopathology and change in weight among children or parents; (3) the associations between change in psychopathology within parent–child dyads. Methods: 172 parent–child dyads participated in 4‐month FBT and were subsequently randomized to one of three 8‐month maintenance interventions. General psychopathology (child anxiety/depressive symptoms, parent severity of global psychological distress), ED psychopathology (shape/weight concern), and percent overweight were assessed at baseline, post‐FBT, and post‐maintenance. Separate linear mixed‐effects models evaluated change in general and ED psychopathology, including an interaction between maintenance condition and time. Partial correlations examined associations between change in psychopathology and percent overweight among children or parents, and associations between change in psychopathology within parent–child dyads. Results: Among children, significant reductions were observed from baseline to post‐FBT in all forms of psychopathology and from post‐FBT to post‐maintenance in general psychopathology. Among parents, significant reductions were observed from baseline to post‐FBT in all forms of psychopathology; reductions were maintained from post‐FBT to post‐maintenance. There was no significant interaction between maintenance condition and time. Correlations between change in most forms of parent or child psychopathology and percent overweight were observed. Conclusions: Participation in FBT and maintenance was associated with improvements in general and ED psychopathology in both parents and children. [ABSTRACT FROM AUTHOR]

Extended-care interventions have been demonstrated to improve maintenance of weight loss after the end of initial obesity treatment; however, it is unclear whether these programs are similarly effective for African American versus White participants. The current study examined differences in effectiveness of individual versus group telephone-based extended-care on weight regain, compared to educational control, in 410 African American (n = 82) and White (n = 328) adults with obesity (mean ± SD age = 55.6 ± 10.3 years, BMI = 36.4 ± 3.7 kg/m2). After controlling for initial weight loss, multivariate linear models demonstrated a significant interaction between treatment condition and race, p =.048. Randomization to the individual telephone condition produced the least amount of weight regain in White participants, while the group condition produced the least amount of weight regain in African American participants. Future research should investigate the role of social support in regain for African American versus White participants and examine whether tailoring delivery format by race may improve long-term outcomes. [ABSTRACT FROM AUTHOR]