Michaela Kiernan

How and Why Criteria Defining Moderators and Mediators Differ Between the Baron & Kenny and MacArthur Approaches

OBJECTIVE In recognition of the increasingly important role of moderators and mediators in clinical research, clear definitions are sought of the two terms to avoid inconsistent, ambiguous, and possibly misleading results across clinical research studies. DESIGN The criteria used to define moderators and mediators proposed by the Baron & Kenny approach, which have been long used in social/behavioral research, are directly compared to the criteria proposed by the recent MacArthur approach, which modified the Baron & Kenny criteria. RESULTS After clarifying the differences in criteria between approaches, the rationale for the modifications is clarified and the implications for the design and interpretation of future studies considered. CONCLUSIONS Researchers may find modifications introduced in the MacArthur approach more appropriate to their research objectives, particularly if their research might have a direct influence on decision making.

Attitudes and practices of pediatric oncology providers regarding fertility issues.

Given the higher survival rates of childhood cancer, health care providers must be aware of the side effects of cancer therapies to educate patients and provide appropriate interventions to reduce cancer‐related morbidity. To understand the current practices and attitudes in a pediatric hematology/oncology clinic, health care providers were surveyed regarding fertility issues pertinent to their patient care.

Characteristics of successful and unsuccessful dieters: an application of signal detection methodology.

Signal detection methods were used to identify predictors of successful weight loss in 177 mildly to moderately overweight women and men assigned to one of two weight-loss programs. Predictors included initial demographic, physiological, behavioral, and psychosocial characteristics, and program type (e.g. diet-only and diet-plus-exercise). Successful weight loss was defined as a loss of at least two units of body mass index at one year. Four subgroups were identified. Participants in the diet-plus-exercise program who were initially more satisfied with their bodies and did not have a history of repeated weight loss were most likely to succeed (63% succeeded). In contrast, participants assigned to the diet-plus-exercise program who were either extremely dissatisfied with their bodies or who had a history of repeated weight loss were at similar risk for failure as participants in the diet-only program (only 26% to 35% succeeded). The results underscore the potential utility of exploring these subgroups further to inform the development of new treatment strategies to increase the likelihood of success.

Concerns about infertility risks among pediatric oncology patients and their parents

Given pediatric cancer patients are living into adulthood, parents and patients need to be informed about fertility‐related side effects of their particular treatment.

Social Support for Healthy Behaviors: Scale Psychometrics and Prediction of Weight Loss Among Women in a Behavioral Program

Social support could be a powerful weight‐loss treatment moderator or mediator but is rarely assessed. We assessed the psychometric properties, initial levels, and predictive validity of a measure of perceived social support and sabotage from friends and family for healthy eating and physical activity (eight subscales). Overweight/obese women randomized to one of two 6‐month, group‐based behavioral weight‐loss programs (N = 267; mean BMI 32.1 ± 3.5; 66.3% White) completed subscales at baseline, and weight loss was assessed at 6 months. Internal consistency, discriminant validity, and content validity were excellent for support subscales and adequate for sabotage subscales; qualitative responses revealed novel deliberate instances not reflected in current sabotage items. Most women (>75%) “never” or “rarely” experienced support from friends or family. Using nonparametric classification methods, we identified two subscales—support from friends for healthy eating and support from family for physical activity—that predicted three clinically meaningful subgroups who ranged in likelihood of losing ≥5% of initial weight at 6 months. Women who “never” experienced family support were least likely to lose weight (45.7% lost weight) whereas women who experienced both frequent friend and family support were more likely to lose weight (71.6% lost weight). Paradoxically, women who “never” experienced friend support were most likely to lose weight (80.0% lost weight), perhaps because the group‐based programs provided support lacking from friendships. Psychometrics for support subscales were excellent; initial support was rare; and the differential roles of friend vs. family support could inform future targeted weight‐loss interventions to subgroups at risk.

Is a Web Survey as Effective as a Mail Survey? A Field Experiment Among Computer Users.

With the exponential increase in Web access, program evaluators need to understand the methodological benefits and barriers of using the Web to collect survey data from program participants. In this experimental study, the authors examined whether a Web survey can be as effective as the more established mail survey on three measures of survey effectiveness: response rate, question completion rate, and the lack of evaluative bias. Community- and university-based educators (n = 274) attending a 2-day program were randomly assigned to receive a Web or mail survey evaluating the program. Among those participants successfully solicited by e-mail, Web survey participants were more likely to respond (95%) than mail survey participants (79%). Web survey participants completed similarly high numbers of quantitative questions as mail survey participants, provided longer and more substantive responses to qualitative questions, and did not demonstrate evidence of evaluative bias. These results suggest that program evaluators could expand their use of Web surveys among computer users.

The effects of marital transitions on changes in physical activity: results from a 10-year community study.

The potential effects of making a marital transition on subsequent physical activity were evaluated across a ten-year period in a population-based sample of 302 women and 256 men ages 25 to 75 years. Subjects completed a structured interview at five timepoints throughout the ten-year period during which they reported on their physical activity level as well as marital status. The transition from a married to a single state did not affect physical activity relative to remaining married when analyses of either slopes or mean values were used. In contrast, the transition from a single to a married state resulted in significant positive changes in physical activity relative to remaining single throughout the study period when physical activity slopes, though not means, were compared. The results suggest that marriage may potentially set the stage for natural changes in physical activity that could be capitalized on through appropriate intervention, but additional research is needed to verify this in light of the inconsistent pattern of findings.

Practices Associated with Weight Loss Versus Weight-Loss Maintenance Results of a National Survey

BACKGROUND Few studies have examined the weight-control practices that promote weight loss and weight-loss maintenance in the same sample. PURPOSE To examine whether the weight control practices associated with weight loss differ from those associated with weight-loss maintenance. METHODS Cross-sectional survey of a random sample of 1165 U.S. adults. The adjusted associations of the use of 36 weight-control practices in the past week with success in weight loss (≥10% lost in the past year) and success in weight-loss maintenance (≥10% lost and maintained for ≥1 year) were examined. RESULTS Of the 36 practices, only 8 (22%) were associated with both weight loss and weight-loss maintenance. Overall, there was poor agreement (kappa=0.22) between the practices associated with weight loss and/or weight-loss maintenance. For example, those who reported more often following a consistent exercise routine or eating plenty of low-fat sources of protein were 1.97 (95% CI=1.33, 2.94) and 1.76 (95% CI=1.25, 2.50) times more likely, respectively, to report weight-loss maintenance but not weight loss. Alternatively, those who reported more often doing different kinds of exercises or planning meals ahead of time were 2.56 (95% CI=1.44, 4.55) and 1.68 (95% CI=1.03, 2.74) times more likely, respectively, to report weight loss but not weight-loss maintenance. CONCLUSIONS Successful weight loss and weight-loss maintenance may require two different sets of practices. Designing interventions with this premise may inform the design of more effective weight-loss maintenance interventions.

Methodologic issues in measuring physical activity and physical fitness when evaluating the role of dietary supplements for physically active people

Physical activity and physical fitness are complex entities comprising numerous diverse components that present a challenge in terms of accurate, reliable measurement. Physical activity can be classified by its mechanical (static or dynamic) or metabolic (aerobic or anaerobic) characteristics and its intensity (absolute or relative to the persons capacity). Habitual physical activity can be assessed by using a variety of questionnaires, diaries, or logs and by monitoring body movement or physiologic responses. Selection of a measurement method depends on the purpose of the evaluation, the nature of the study population, and the resources available. The various components of physical fitness can be assessed accurately in the laboratory and, in many cases, in the field by using a composite of performance tests. Most coaches and high-level athletes would accept as very beneficial a dietary supplement that would increase performance in a competitive event by even 3%; for example, lowering a runners time of 3 min, 43 s in the 1500 m by 6.7 s. To establish that such small changes are caused by the dietary supplement requires carefully conducted research that involves randomized, placebo-controlled, double-blind studies designed to maximize statistical power. Statistical power can be increased by enlarging sample size, selecting tests with high reliability, selecting a potent but safe supplement, and maximizing adherence. Failure to design studies with adequate statistical power will produce results that are unreliable and will increase the likelihood that a true effect will be missed.

Physical Activity as a Nonpharmacological Treatment for Depression: A Review

Physical activity is increasingly being cited as an alternative to more traditional drug treatments for treating depression. Although an increasing amount of research has investigated this theory, much of the literature has been criticized from a methodological perspective. Given rising concern for the increasing costs of mental health care, it is timely and important to examine valid, reliable, and objective research findings on the potential role of physical activity as a low-cost non-pharmacological intervention for the treatment of depression. This article reviews cross-sectional, longitudinal, and randomized studies that investigated the role of physical activity in the prevention and alleviation of depression. The review found that although there is undoubtedly a need for more research with a greater emphasis on methodological strength, the scientific literature is generally supportive of the beneficial effects of aerobic and nonaerobic exercise on depression in clinically and nonclinically depressed adults. Implications for public health are discussed.