Biomedical subjects

David M Murray

Publications and source records attributed to David M Murray.

At least 37 records · Page 2Linked to original sources

PubMed2004

Assessing intervention effects in a school-based nutrition intervention trial: which analytic model is most powerful?

This article compares four mixed-model analyses valid for group-randomized trials (GRTs) involving a nested cohort design with a single pretest and posttest. This study makes estimates of intraclass correlations (ICCs) available to investigators planning GRTs addressing dietary outcomes. It also provides formulae demonstrating the potential benefits to the standard error of the intervention effect (sigma(delta)) from adjustments for both fixed and time-varying covariates and correlations over time. These estimates will allow other researchers using these variables to plan their studies by estimating a priori detectable differences and sample size requirements for any of the four analytic options. These methods are demonstrated using data from the Teens Eating for Energy and Nutrition at School study. Mixed-model analyses of covariance proved to be the most powerful analysis in that data set. The formulae may be applied to any dependent variable in any GRT given corresponding information for those variables on the parameters that define the formulae.

Adolescent↗

PubMed2004

School-level intraclass correlation for physical activity in adolescent girls.

PURPOSE: The Trial for Activity in Adolescent Girls (TAAG) is a multi-center group-randomized trial to reduce the usual decline in moderate to vigorous physical activity (MVPA) among middle-school girls. In group-randomized trials, the group-level intraclass correlation (ICC) has a strong inverse relationship to power and a good estimate of ICC is needed to determine sample size. As a result, we conducted a substudy to estimate the school-level ICC for intensity-weighted minutes of MVPA measured using an accelerometer. METHODS: To estimate the ICC, each of six sites recruited two schools and randomly selected 45 eighth grade girls from each school; 80.7% participated. Each girl wore an Actigraph accelerometer for 7 d. Readings above 1500 counts per half minute were counted as MVPA. These counts were converted into metabolic equivalents (MET) and summed over 6 a.m. to midnight to provide MET-minutes per 18-h day of MVPA. Minutes of MVPA per 18-h day also were calculated ignoring the MET value. RESULTS: The unadjusted school-level ICC for minutes of MVPA was 0.0205 (95%CI: -0.0079, 0.1727) and for MET-minutes of MVPA was 0.0045 (95% CI: -0.0147, 0.1145). Adjustment for age and BMI had no measurable effect, whereas adjustment for ethnicity reduced both ICC; adjusted values were 0.0175 (95% CI: -0.0092, 0.1622) for minutes of MVPA and 0.0000 (95% CI: -0.0166, 0.0968) for MET-minutes of MVPA. This information was used to calculate the number of schools and girls needed for TAAG to have 90% power to detect a 50% reduction in the decline of MET-minutes of MVPA between sixth and eighth grade. CONCLUSIONS: The results called for 36 schools in TAAG, with 120 girls invited for measurements at each school, and a minimum participation rate of 80%.

Acceleration↗

PubMed2004

Design and analysis of group-randomized trials: a review of recent practices.

We reviewed group-randomized trials (GRTs) published in the American Journal of Public Health and Preventive Medicine from 1998 through 2002 and estimated the proportion of GRTs that employ appropriate methods for design and analysis. Of 60 articles, 9 (15.0%) reported evidence of using appropriate methods for sample size estimation. Of 59 articles in the analytic review, 27 (45.8%) reported at least 1 inappropriate analysis and 12 (20.3%) reported only inappropriate analyses. Nineteen (32.2%) reported analyses at an individual or subgroup level, ignoring group, or included group as a fixed effect. Hence increased vigilance is needed to ensure that appropriate methods for GRTs are employed and that results based on inappropriate methods are not published.

Bibliometrics↗

PubMed2004

Design and analysis of group-randomized trials: a review of recent methodological developments.

We review recent developments in the design and analysis of group-randomized trials (GRTs). Regarding design, we summarize developments in estimates of intraclass correlation, power analysis, matched designs, designs involving one group per condition, and designs in which individuals are randomized to receive treatments in groups. Regarding analysis, we summarize developments in marginal and conditional models, the sandwich estimator, model-based estimators, binary data, survival analysis, randomization tests, survey methods, latent variable methods and nonlinear mixed models, time series methods, global tests for multiple endpoints, mediation effects, missing data, trial reporting, and software. We encourage investigators who conduct GRTs to become familiar with these developments and to collaborate with methodologists who can strengthen the design and analysis of their trials.

Cluster Analysis↗

PubMed2004

Defining accelerometer thresholds for activity intensities in adolescent girls.

PURPOSE: To derive a regression equation that estimates metabolic equivalent (MET) from accelerometer counts, and to define thresholds of accelerometer counts that can be used to delineate sedentary, light, moderate, and vigorous activity in adolescent girls. METHODS: Seventy-four healthy 8th grade girls, age 13 - 14 yr, were recruited from urban areas of Baltimore, MD, Minneapolis/St. Paul, MN, and Columbia, SC, to participate in the study. Accelerometer and oxygen consumption (.-)VO(2)) data for 10 activities that varied in intensity from sedentary (e.g., TV watching) to vigorous (e.g., running) were collected. While performing these activities, the girls wore two accelerometers, a heart rate monitor and a Cosmed K4b2 portable metabolic unit for measurement of (.-)VO(2). A random-coefficients model was used to estimate the relationship between accelerometer counts and (.-)VO(2). Activity thresholds were defined by minimizing the false positive and false negative classifications. RESULTS: The activities provided a wide range in (.-)VO(2) (3 - 36 mL x kg x min) with a correspondingly wide range in accelerometer counts (1- 3928 counts x 30 s). The regression line for MET score versus counts was MET = 2.01 +/- 0.00171 (counts x 30 s) (mixed model R = 0.84, SEE = 1.36). A threshold of 1500 counts x 30 s defined the lower end of the moderate intensity (approximately 4.6 METs) range of physical activity. That cutpoint distinguished between slow and brisk walking, and gave the lowest number of false positive and false negative classifications. The threshold ranges for sedentary, light, moderate, and vigorous physical activity were found to be 0 - 50, 51- 1499, 1500 - 2600, and >2600 counts x 30 s, respectively. CONCLUSION: The developed equation and these activity thresholds can be used for prediction of MET score from accelerometer counts and participation in various intensities of physical activity in adolescent girls.

Acceleration↗

PubMed2004

Physical activity in relation to all-site and lung cancer incidence and mortality in current and former smokers.

Increased physical activity has been associated with a reduction in the incidence and mortality from all-site cancer and some site-specific cancers in samples of primarily nonsmoking individuals; however, little is known about whether physical activity is associated with similar risk reductions among smokers and ex-smokers. This study examined physical activity in relation to all-site cancer and lung cancer incidence and mortality in a sample of current and former smokers (n = 7,045; 59% male; 95% Caucasian; mean age, 63 years) drawn from the beta-Carotene and Retinol Efficacy Trial, a lung cancer chemoprevention trial. Hazard rate ratios and 95% confidence intervals associated with a 1 SD increase in physical activity were 0.86 (0.80-0.94) for all-site cancer only among men, 0.84 (0.69-1.03) for lung cancer only for younger participants, 0.75 (0.59-0.94) for cancer mortality among younger participants and 0.68 (0.53-0.89) among women, and 0.69 (0.53-0.90) for lung cancer mortality only among women. These results suggest that incidence may be more attenuated by physical activity for men and mortality more attenuated for women. Effects may be more pronounced for younger people and may differ inconsistently by pack-years of smoking. Physical activity may play a role in reducing cancer risk and mortality among those with significant tobacco exposure. Prospective studies using more sophisticated measures of physical activity assessed at multiple time points during follow-up are needed to corroborate these associations.

Age Factors↗

PubMed2003

Evaluation of the American Stop Smoking Intervention Study (ASSIST): a report of outcomes.

BACKGROUND: The National Cancer Institute funded an 8-year, nonrandomized demonstration project for tobacco prevention and control, the American Stop Smoking Intervention Study (ASSIST). To evaluate ASSIST, we compared changes in adult smoking prevalence, per capita cigarette consumption, and tobacco control policies between the 17 ASSIST states and the 33 non-ASSIST states and the District of Columbia. METHODS: The strength of tobacco control index was used to measure state-level program elements directed at tobacco control, and the initial outcomes index (IOI) was used to measure states' tobacco control policy outcomes. Prevalence data were obtained from the Tobacco Use Supplement to the Current Population Survey, and consumption data were obtained from the Tobacco Institute's bimonthly sales figures for cigarette packs moved from wholesale warehouses. Two-stage regression and mixed-effects linear modeling were used to analyze the various outcomes. Statistical analyses for testing individual regression coefficients were one-sided. RESULTS: ASSIST states had a greater decrease in adult smoking prevalence than non-ASSIST states, with an adjusted difference of -0.63% (P =.049). Per capita cigarette consumption was not statistically significantly different between ASSIST and non-ASSIST states. However, an increase in the IOI of a state from the 25th to the 75th percentile was associated with a reduction in per capita cigarette consumption by 0.57 packs per person per month. State IOI was also inversely, albeit not statistically significantly, associated with smoking prevalence (regression coefficient = -0.11;P =.06). CONCLUSIONS: The reduction in adult smoking prevalence associated with ASSIST could have translated into approximately 278 700 fewer smokers nationwide if all states had implemented ASSIST. Investment in building state-level tobacco control capacity and promoting changes in tobacco control policies are effective strategies for reducing tobacco use.

Adolescent↗

PubMed2003

Design, implementation, and quality control in the Pathways American-Indian multicenter trial.

BACKGROUND: Pathways was the first multicenter American-Indian school-based study to test the effectiveness of an obesity prevention program promoting healthy eating and physical activity. METHODS: Pathways employed a nested cohort design in which 41 schools were randomized to intervention or control conditions and students within these schools were followed as a cohort (1,704 third graders at baseline). The study's primary endpoint was percent body fat. Secondary endpoints were levels of fat in school lunches; time spent in physical activity; and knowledge, attitudes, and behaviors regarding diet and exercise. Quality control (QC) included design of data management systems which provided standardization and quality assurance of data collection and processing. Data QC procedures at study centers included manuals of operation, training and certification, and monitoring of performance. Process evaluation was conducted to monitor dose and fidelity of the interventions. Registration and tracking systems were used for students and schools. RESULTS: No difference in mean percent body fat at fifth grade was found between the intervention and control schools. Percent of calories from fat and saturated fat in school lunches was significantly reduced in the intervention schools as was total energy intake from 24-hour recalls. Significant increases in self-reported physical activity levels and knowledge of healthy behaviors were found for the intervention school students. CONCLUSIONS: The Pathways study results provide evidence demonstrating the role schools can play in public health promotion. Its study design and QC systems and procedures provide useful models for other similar school based multi- or single-site studies.

Child↗

PubMed2003

The impact of the Pathways intervention on psychosocial variables related to diet and physical activity in American Indian schoolchildren.

BACKGROUND: The purpose of this study was to examine the impact of the Pathways intervention on pychosocial variables related to physical activity and diet in American Indian children. METHODS: Schools serving American Indian children were randomized to a multicomponent intervention or control condition. At baseline (fall of third grade) and in the spring semester of third, fourth, and fifth grades 755 boys and 692 girls completed a classroom-administered questionnaire. The questionnaire assessed self-efficacy, knowledge, and behavioral intentions related to diet and physical activity, as well as weight loss behaviors and body image. RESULTS: Knowledge of nutrition and physical activity messages increased in both boys and girls in the intervention group compared to controls; however, knowledge of which foods contained more fat did not increase consistently. Compared to controls, self-efficacy to be physically active increased among girls in intervention schools, but not among boys, whereas self-efficacy to make more healthy food choices did not increase more than in controls in either gender. In the intervention group, compared to controls, healthy food intentions and participation in physically active behaviors increased in both boys and girls. Perception of healthy body size and weight loss attempts did not differ in the intervention and control groups. CONCLUSION: The Pathways intervention program had a positive impact on several aspects of obesity-related knowledge, attitudes, and behaviors.

Child↗

PubMed2003

Rapid progression to regular cigarette smoking among nonsmoking adolescents: interactions with gender and ethnicity.

BACKGROUND: While the correlates and predictors associated with transition through the stages of smoking acquisition have received substantial attention, the identification of factors associated with the time course of progression remain generally unexplored. METHODS: We identified adolescents escalating from nonsmoking to regular smoking in 1 year as rapid progressors (n = 98) and those escalating from nonsmoking to experimental smoking in 1 year as slow progressors (n = 555). We entered demographic and psychosocial variables, initial reactions to smoking variables, and their interactions with gender and ethnicity into a logistic regression analysis comparing rapid progressors to slow progressors. RESULTS: At baseline, rapid progressors reported more friends who smoked regularly. Girls who reported more concern with dieting and less social success were more likely to progress to regular smoking within 1 year; these variables did not influence progression in boys. Those who associated positive feelings with their initial smoking experience were more likely to progress to regular smoking. Differences between white and African American youth emphasize the importance of physiological interpretations of initial smoking experiences. CONCLUSIONS: Our findings suggest that even as nonsmokers, adolescents likely to progress quickly to regular smoking can be identified. Researchers designing prevention programs should take these factors into account.

Adolescent↗

PubMed2003

Relationships among smoking status, ethnicity, socioeconomic indicators, and lifestyle variables in a biracial sample of women.

BACKGROUND: Smoking prevalence rates remain high among women and smoking initiation has increased for young adults. Little is known about the unique patterns of smoking, risk factors, and correlates of quitting in Black versus White women of child-bearing age. METHOD: This study examined the relationships among smoking, ethnicity, socioeconomic status (SES), and lifestyle variables among 715 women (43.6% Blacks and 56.4% Whites). Stringent inclusion criteria were used for ethnicity, which allows for distinct comparisons but may reduce generalizability of results. RESULTS: Black current smokers smoked fewer cigarettes per day and reported initiating smoking at a later age than Whites. Current versus never smoking was associated with income, education, and caffeine intake. There was a significant ethnicity by alcohol interaction (at lower levels of alcohol intake Whites were more likely to smoke but at higher levels of alcohol there were no ethnic differences). Former smoking versus current smoking was associated with alcohol intake, education, and pack years of smoking. CONCLUSIONS: The results of the study suggest several ethnic differences in smoking patterns as well as several correlates of smoking status. These results have implications for the tailoring of interventions and illustrate the association of other health risk factors with smoking status.

Adult↗

PubMed2003

Evaluating the Lions-Quest "Skills for Adolescence" drug education program. Second-year behavior outcomes.

Thirty-four schools (n=7426 consented sixth graders, 71% of the eligible population) were randomized to conditions to test the hypothesis that Skills for Adolescence (SFA), a widely used comprehensive life skills training curriculum with a dedicated drug education unit, is more effective than standard care in deterring and delaying substance use through middle school. Two-year posttest (1-year post-intervention) data were collected from 5691 eighth graders (77% of those who completed the sixth-grade survey and 87% of those who completed the seventh-grade survey). Lifetime and recent (last 30 days) use of five substances or combinations of substances was compared using mixed-model regression to control for school clustering. There were two significant treatment main effects at the end of the eighth grade: lifetime (P=.05) and recent (P<.03) marijuana use were lower in SFA than control schools with pretest usage and salient demographic and psychosocial variables controlled. There was also one significant Treatment x Pretest Usage interaction around binge drinking. Baseline binge drinkers in SFA schools were less likely to report recent binge drinking than students in control schools (P<.01); there were no treatment differences among baseline nonbinge drinkers. Analyses of potential mediators of SFA treatment effects on eighth-grade binge drinking and marijuana use suggested that SFA increased self-efficacy around drug refusal skills, but did not affect behavioral intentions, perceptions of harm, or perceived peer norms. These 2-year (1-year post-intervention) outcomes offer some additional support for SFA effectiveness and the general thrust of school-based, life skills-based prevention programs. The promising sixth- through eighth-grade findings for SFA, a commercially available program, provide a further step in bridging a major gap in the "research to practice" literature: theory-based interventions that have documented behavioral effects have not enjoyed large-scale implementation, while intuition-based programs that have no documented effects still enjoy wide exposure.

Adolescent↗

PubMed2003

The reliability and predictive value of adolescents' reports of initial reactions to smoking.

A sample of 372 adolescents completed annual surveys regarding their initial reactions to smoking (IRTS) and their current smoking status. Each annual survey asked participants if they had the following five reactions the first time they smoked a cigarette: coughing, or feeling dizzy, sick, high, or relaxed. Time 1 IRTS data were collected within 1 year of the reported initial smoking experience, and Time 2 IRTS data were collected 1 year later. Kappa values for two IRTS items, coughing (.45) and dizziness (.40), indicated modest but acceptable reliability across a 1-year period, but the remaining items showed poor reliability (all < or =.31). Logistic regression analyses indicated that no IRTS item significantly predicted regular (at least weekly) smoking 1 year later. However, when IRTS and smoking status were assessed concurrently (at Time 2), reports of feeling relaxed and not coughing during the initial episode were significantly correlated with regular smoking. Participants who progressed from experimental to regular smoking from Time 1 to Time 2 were more likely to report relaxation as an initial reaction to smoking at Time 2 after denying relaxation at Time 1.

Adolescent↗

PubMed2003

School functioning and violent behavior among young adolescents: a contextual analysis.

This paper examines associations between overall school functioning and frequency of violent behaviors among young adolescents (ages 10-14). The sample included 16 middle schools participating in an unrelated intervention study (on nutrition) in Minneapolis, Minnesota. A School Functioning Index, developed to characterize schools' overall stability, performance and demographics, was constructed using data from public archives and school administrator surveys. Data on violent behaviors and other variables were collected in student surveys in fall 1998 and spring 1999. We used multilevel modeling to assess the effect of school functioning on violent behavior after adjusting for known individual-level covariates of violent behaviors. We found an interaction between school functioning (group-level variable) and expectations for future education (individual-level variable). Among students who reported expectations of completing a college degree (71% of the sample), positive school functioning was negatively associated with violent behaviors. Among students that reported expectations of completing less than a college degree, no association was found between school functioning and violent behaviors. These results support earlier work suggesting that objectively measured school characteristics are associated with students' violent behaviors even after accounting for individual-level factors and also identify a subgroup of students for whom school detachment may be an issue.

Adolescent↗

PubMed2003

Methods to reduce the impact of intraclass correlation in group-randomized trials.

This study reports intraclass correlation (ICC) for dependent variables used in group-randomized trials (GRTs). The authors also document the effect of two methods suggested to reduce the impact of ICC in GRTs; these two methods are modeling time and regression adjustment for covariates. They coded and analyzed 1,188 ICC estimates from 17 published, in press, and unpublished articles representing 21 studies. Findings confirm that both methods can improve the efficiency of analyses shown to be valid across conditions common in GRTs. Investigators planning GRTs should obtain ICC estimates matched to their planned analysis so that they can size their studies properly.

Analysis of Variance↗

PubMed2003

Child- and parent-targeted interventions: the Memphis GEMS pilot study.

OBJECTIVE: To assess the feasibility, acceptability, and outcomes of 2 versions of a culturally relevant, family-based intervention to prevent excess weight gain in pre-adolescent African-American girls. DESIGN: Three-arm, 12-week parallel group randomized controlled pilot trial. SETTING: Community centers in Memphis, Tennessee. PARTICIPANTS: Sixty African-American girls, aged 8 to 10 years, with a body mass index (BMI) > or = 25th percentile of the CDC growth charts, along with their parents/caregivers. INTERVENTIONS: The active interventions involved highly interactive weekly group sessions with either girls (child-targeted program) or parents/caregivers (parent-targeted program). Content focused on knowledge and behavior change skills to promote healthy eating and increased physical activity. The comparison intervention focused on global self-esteem. MAIN OUTCOME MEASURES: Given the lack of power and the limited time frame of the pilot study, outcomes were evaluated on the basis of implementation measures and changes in physical activity (accelerometer data), and in consumption of sweetened beverages and water, as estimated from questionnaires. Changes in body mass index, waist circumference, and body composition were also examined. RESULTS: The Memphis GEMS pilot intervention met all recruitment, retention, implementation, and participation goals, and was given high rating by both participants and interventionists. With respect to the comparison intervention, girls in both the child-targeted and parent-targeted interventions demonstrated a trend toward reduced body mass index and waist circumference. In addition, girls in the active intervention groups reduced their consumption of sweetened beverages by 34%, increased their level of moderate-to-vigorous activity by 12%, and increased their serving; of water by 1.5%. CONCLUSIONS: The findings from this pilot study demonstrated the feasibility, perceived acceptability, and efficacy of culturally relevant, obesity prevention interventions for pre-adolescent African-American girls and their parents/caregivers.

Adult↗

PubMed2002

History of sport participation in relation to obesity and related health behaviors in women.

BACKGROUND: Organized sport participation in youth is a common form of physical activity; yet, little is known about how it is associated with adult obesity and related health behaviors. The purpose of this study was to investigate whether a history of youth sport participation was related to adult obesity, physical activity, and dietary intake among women. METHODS: Participating women (209 African American, 277 Caucasian; ages 18-39), recruited from the community, completed laboratory measures, a paper and pencil survey assessing past sport participation and current physical activity level, and dietary records. RESULTS: Linear regression revealed that a history of sport participation predicted lower adult body mass index and higher total and sport activity levels for both ethnic groups and higher work-related physical activity among Caucasians (all P < 0.001). Past sports participation did not predict dietary intake. CONCLUSIONS: The results suggest that girls' participation in sports may lay the foundation for adult health and health behaviors and that sports participation could be an important component of obesity prevention programs.

Adolescent↗

PubMed2002

Psychosocial correlates of physical activity and sedentary leisure habits in young adolescents: the Teens Eating for Energy and Nutrition at School study.

BACKGROUND: Low levels of physical activity (PA) and highly sedentary leisure habits (SLH) in youth may establish behavioral patterns that will predispose youth to increased chronic disease risk in adulthood. The purpose of this paper was to examine associations of demographic and psychosocial factors with self-reported PA and SLH in young adolescents. METHODS: A general linear mixed model predicted self-reported PA and SLH in the spring from demographic and psychosocial variables measured the previous fall in 3798 seventh grade students. RESULTS: PA and SLH differed by race, with Caucasian students reporting among the highest PA and lowest SLH. Perceptions of higher academic rank or expectations predicted higher PA and lower SLH. Depressive symptomatology predicted higher SLH scores but not PA. Higher self-reported value of health, appearance, and achievement predicted higher PA and lower SLH in girls. Girls who reported that their mothers had an authoritative parenting style also reported higher PA and lower SLH. CONCLUSIONS: Determinants of PA and SLH appear to differ from each other, particularly in boys. Development of effective programs to increase PA and/or decrease SLH in young adolescents should be based on a clear understanding of the determinants of these behaviors.

Adolescent↗