Statistical power as a function of Cronbach alpha of instrument questionnaire items

Abstract Background In countless number of clinical trials, measurements of outcomes rely on instrument questionnaire items which however often suffer measurement error problems which in turn affect statistical power of study designs. The Cronbach alpha or coefficient alpha, here denoted by C α , can be used as a measure of internal consistency of parallel instrument items that are developed to measure a target unidimensional outcome construct. Scale score for the target construct is often represented by the sum of the item scores. However, power functions based on C α have been lacking for various study designs. Methods We formulate a statistical model for parallel items to derive power functions as a function of C α under several study designs. To this end, we assume fixed true score variance assumption as opposed to usual fixed total variance assumption. That assumption is critical and practically relevant to show that smaller measurement errors are inversely associated with higher inter-item correlations, and thus that greater C α is associated with greater statistical power. We compare the derived theoretical statistical power with empirical power obtained through Monte Carlo simulations for the following comparisons: one-sample comparison of pre- and post-treatment mean differences, two-sample comparison of pre-post mean differences between groups, and two-sample comparison of mean differences between groups. Results It is shown that C α is the same as a test-retest correlation of the scale scores of parallel items, which enables testing significance of C α . Closed-form power functions and samples size determination formulas are derived in terms of C α , for all of the aforementioned comparisons. Power functions are shown to be an increasing function of C α , regardless of comparison of interest. The derived power functions are well validated by simulation studies that show that the magnitudes of theoretical power are virtually identical to those of the empirical power. Conclusion Regardless of research designs or settings, in order to increase statistical power, development and use of instruments with greater C α , or equivalently with greater inter-item correlations, is crucial for trials that intend to use questionnaire items for measuring research outcomes. Discussion Further development of the power functions for binary or ordinal item scores and under more general item correlation strutures reflecting more real world situations would be a valuable future study

Associations of Appetitive Traits and Parental Feeding Style with Diet Quality During Early Childhood.

BackgroundAppetitive traits and parent feeding styles are associated with body mass index in children, yet their associations with child diet quality are unclear.ObjectiveThe objective was to examine relations of appetitive traits and parental feeding style with diet quality in 3.5-year-old children.DesignThe study was a secondary, cross-sectional analysis of data from Sprouts, a follow-up study of the Pregnancy Eating Attributes Study (PEAS). Birthing parents completed the Child Eating Behavior Questionnaire, Caregiver's Feeding Styles Questionnaire, and proxy 24-hour dietary recalls for their children from February 2019 to December 2020.Participants/settingParticipants were 162 birthing parents (early pregnancy BMI ≥18.5 kg/m2 and absence of pre-existing diabetes, any medical condition contraindicating study participation, self-reported eating disorder, and medications that could affect diet or weight) and their children living in North Carolina.Main outcome measuresHealthy Eating Index-2015 (HEI-2015) total scores were calculated.Statistical analyses performedPath modeling was conducted using PROC CALIS with full information maximum likelihood (FIML) to account for missing data (ResultsA 1-SD greater food fussiness was associated with a 2.4-point lower HEI-2015 total score [p = .02, 95% CI (-4.32, -0.48)] in children. When parental feeding style was authoritarian, a 1-SD greater food responsiveness was associated a 4.1-point higher HEI-2015 total score [p = .007, 95% CI (1.12, 7.01)] in children. When parental feeding style was authoritative, a 1-SD greater slowness in eating was associated with a 5.8-point lower HEI-2015 total score [p = .01, 95% CI (-10.26, -1.33)] in children.ConclusionsParental feeding style may modify the association of appetitive traits with diet quality in young children. Future research could determine whether matching parent feeding styles to child appetitive trait profiles improves child diet quality

Parental feeding practices and associations with child weight status. Swedish validation of the Child Feeding Questionnaire finds parents of 4-year-olds less restrictive

The Child Feeding Questionnaire (CFQ) assesses parental feeding attitudes, beliefs and practices concerned with child feeding and obesity proneness. The questionnaire has been developed in the U.S. ..

Developmental trajectory of appetitive traits and their bidirectional relations with body mass index from infancy to early childhood.

Appetitive traits, including food responsiveness, enjoyment of food, satiety responsiveness and slowness in eating, are associated with childhood body mass index. Change in appetitive traits from infancy to childhood and the direction of causality between appetitive traits and body mass index are unclear. The present study examined the developmental trajectory of appetitive traits and their bidirectional relations with body mass index, from infancy to early childhood. Mothers in the Pregnancy Eating Attributes Study and follow-up (n = 162) reported child appetitive traits using the Baby and Child Eating Behaviour Questionnaires at ages 6 months and 3.5 years, respectively. Standardized body mass index (zBMI) was calculated from child anthropometrics. Cross-lagged panel models estimated bidirectional relations between appetitive traits and zBMI. Food responsiveness, satiety responsiveness and slowness in eating increased from infancy to early childhood. In cross-lagged panel models, lower infant satiety responsiveness (B ± SE = -0.45 ± 0.19, p = .02) predicted greater child zBMI. Infant zBMI did not predict child appetitive traits (p-values >.36). From infancy to early childhood, appetitive traits may amplify. Appetitive traits, particularly satiety responsiveness, appear to influence body mass index during this period, suggesting early intervention targeting these traits may reduce childhood obesity

Ignoring regression to the mean leads to unsupported conclusion about obesity

Abstract Childhood obesity remains a substantial health concern for our population and thoughtful attempts to develop and evaluate the utility of programs to reduce childhood obesity levels are needed. Unfortunately, we believe the conclusion by Burke et al. that the HealthMPowers program produces positive change in body composition is incorrect because the results obtained are likely due to regression to the mean (RTM), a well-known threat to the validity of studies that is often overlooked. Using empirical data, we demonstrate that RTM is likely to be the cause for the changes reported. A more reasonable conclusion than the one of effectiveness the authors offered would be that the results did not support the effectiveness of the intervention. Public health officials, parents, school leaders, community leaders, and regulators need and deserve valid evidence free from spin on which they can base decisions

Recruitment and retention in obesity prevention and treatment trials targeting minority or low-income children: a review of the clinical trials registration database

Abstract Background Efforts to recruit and retain participants in clinical trials are challenging, especially in studies that include minority or low-income children. To date, no studies have systematically examined recruitment and retention strategies and their effectiveness in working successfully with this population. We examined strategies employed to recruit or retain minority or low-income children in trials that included an obesity-related behavior modification component. Methods First, completed home-, community-, and school-based trials involving minority or low-income children aged 2–17 years were identified in a search of the ClinicalTrials.gov registry. Second, a PubMed search of identified trials was conducted to locate publications pertinent to identified trials. Recruitment and retention rates were calculated for studies that included relevant information. Results Our final analytic sample included 43 studies. Of these, 25 studies reported recruitment or retention strategies, with the amount of information varying from a single comment to several pages; 4 published no specific information on recruitment or retention; and 14 had no publications listed in PubMed. The vast majority (92 %) of the 25 studies reported retention rates of, on average, 86 %. Retention rates were lower in studies that: targeted solely Hispanics or African Americans (vs. mixed races of African Americans, whites, and others); involved children and parents (vs. children only); focused on overweight or obese children (vs. general children), lasted ≥1 year (vs. <1 year), were home or community-based (vs. school-based), included nutrition and physical activity intervention (vs. either intervention alone), had body mass index or other anthropometrics as primary outcome measures (vs. obesity-related behavior, insulin sensitivity, etc.). Retention rates did not vary based on child age, number of intervention sessions, or sample size. Conclusions Variable amounts of information were provided on recruitment and retention strategies in obesity-related trials involving minority or low-income children. Although reported retention rates were fairly high, a lack of reporting limited the available information. More and consistent reporting and systematic cataloging of recruitment and retention methods are needed. In addition, qualitative and quantitative studies to inform evidence-based decisions in the selection of effective recruitment and retention strategies for trials including minority or low-income children are warranted

Effects of COVID-19 Lockdown on Lifestyle Behaviors in Children with Obesity Living in Verona, Italy: A Longitudinal Study

Objective: The aim of this study was to test the hypothesis that youths with obesity, when removed from structured school activities and confined to their homes during the coronavirus disease 2019 pandemic, will display unfavorable trends in lifestyle behaviors. Methods: The sample included 41 children and adolescents with obesity participating in a longitudinal observational study located in Verona, Italy. Lifestyle information including diet, activity, and sleep behaviors was collected at baseline and 3 weeks into the national lockdown during which home confinement was mandatory. Changes in outcomes over the two study time points were evaluated for significance using paired t tests. Results: There were no changes in reported vegetable intake; fruit intake increased (P = 0.055) during the lockdown. By contrast, potato chip, red meat, and sugary drink intakes increased significantly during the lockdown (P value range, 0.005 to &lt; 0.001). Time spent in sports activities decreased by 2.30 (SD 4.60) h/wk (P = 0.003), and sleep time increased by 0.65 (SD 1.29) h/d (P = 0.003). Screen time increased by 4.85 (SD 2.40) h/d (P &lt; 0.001). Conclusions: Recognizing these adverse collateral effects of the coronavirus disease 2019 pandemic lockdown is critical in avoiding depreciation of weight control efforts among youths afflicted with excess adiposity. Depending on duration, these untoward lockdown effects may have a lasting impact on a child's or adolescent's adult adiposity level

Infant BMI or Weight-for-Length and Obesity Risk in Early Childhood

Weight-for-length (WFL) is currently used to assess adiposity under 2 years. We assessed WFL- versus BMI-based estimates of adiposity in healthy infants in determining risk for early obesity

Trial Characteristics and Appropriateness of Statistical Methods Applied for Design and Analysis of Randomized School-Based Studies Addressing Weight-Related Issues: A Literature Review

Objective. To evaluate whether clustering effects, often quantified by the intracluster correlation coefficient (ICC), were appropriately accounted for in design and analysis of school-based trials. Methods. We searched PubMed and extracted variables concerning study characteristics, power analysis, ICC use for power analysis, applied statistical models, and the report of the ICC estimated from the observed data. Results. N = 263 papers were identified, and N = 121 papers were included for evaluation. Overall, only a minority (21.5%) of studies incorporated ICC values for power analysis, fewer studies (8.3%) reported the estimated ICC, and 68.6% of studies applied appropriate multilevel models. A greater proportion of studies applied the appropriate models during the past five years (2013-2017) compared to the prior years (74.1% versus 63.5%, p = 0.176). Significantly associated with application of appropriate models were a larger number of schools (p = 0.030), a larger sample size (p = 0.002), longer follow-up (p = 0.014), and randomization at a cluster level (p &lt; 0.001) and so were studies that incorporated the ICC into power analysis (p = 0.016) and reported the estimated ICC (p = 0.030). Conclusion. Although application of appropriate models has increased over the years, consideration of clustering effects in power analysis has been inadequate, as has report of estimated ICC. To increase rigor, future school-based trials should address these issues at both the design and analysis stages