Continued contact and monitoring as follow-up strategies: a long-term study of obesity treatment

Strategies to improve retention in randomised trials

BACKGROUND

Poor retention of participants in randomised trials can lead to missing outcome data which can introduce bias and reduce study power, affecting the generalisability, validity and reliability of results. Many strategies are used to improve retention but few have been formally evaluated.

OBJECTIVES

To quantify the effect of strategies to improve retention of participants in randomised trials and to investigate if the effect varied by trial setting.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Scopus, PsycINFO, CINAHL, Web of Science Core Collection (SCI-expanded, SSCI, CPSI-S, CPCI-SSH and ESCI) either directly with a specified search strategy or indirectly through the ORRCA database. We also searched the SWAT repository to identify ongoing or recently completed retention trials. We did our most recent searches in January 2020.

SELECTION CRITERIA

We included eligible randomised or quasi-randomised trials of evaluations of strategies to increase retention that were embedded in 'host' randomised trials from all disease areas and healthcare settings. We excluded studies aiming to increase treatment compliance.

DATA COLLECTION AND ANALYSIS

We extracted data on: the retention strategy being evaluated; location of study; host trial setting; method of randomisation; numbers and proportions in each intervention and comparator group. We used a risk difference (RD) and 95% confidence interval (CI) to estimate the effectiveness of the strategies to improve retention. We assessed heterogeneity between trials. We applied GRADE to determine the certainty of the evidence within each comparison.

MAIN RESULTS

We identified 70 eligible papers that reported data from 81 retention trials. We included 69 studies with more than 100,000 participants in the final meta-analyses, of which 67 studies evaluated interventions aimed at trial participants and two evaluated interventions aimed at trial staff involved in retention. All studies were in health care and most aimed to improve postal questionnaire response. Interventions were categorised into broad comparison groups: Data collection; Participants; Sites and site staff; Central study management; and Study design. These intervention groups consisted of 52 comparisons, none of which were supported by high-certainty evidence as determined by GRADE assessment. There were four comparisons presenting moderate-certainty evidence, three supporting retention (self-sampling kits, monetary reward together with reminder or prenotification and giving a pen at recruitment) and one reducing retention (inclusion of a diary with usual follow-up compared to usual follow-up alone). Of the remaining studies, 20 presented GRADE low-certainty evidence and 28 presented very low-certainty evidence. Our findings do provide a priority list for future replication studies, especially with regard to comparisons that currently rely on a single study.

AUTHORS' CONCLUSIONS

Most of the interventions we identified aimed to improve retention in the form of postal questionnaire response. There were few evaluations of ways to improve participants returning to trial sites for trial follow-up. None of the comparisons are supported by high-certainty evidence. Comparisons in the review where the evidence certainty could be improved with the addition of well-done studies should be the focus for future evaluations.

Strategies to improve retention in randomised trials

BACKGROUND

Loss to follow-up from randomised trials can introduce bias and reduce study power, affecting the generalisability, validity and reliability of results. Many strategies are used to reduce loss to follow-up and improve retention but few have been formally evaluated.

OBJECTIVES

To quantify the effect of strategies to improve retention on the proportion of participants retained in randomised trials and to investigate if the effect varied by trial strategy and trial setting.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, PreMEDLINE, EMBASE, PsycINFO, DARE, CINAHL, Campbell Collaboration's Social, Psychological, Educational and Criminological Trials Register, and ERIC. We handsearched conference proceedings and publication reference lists for eligible retention trials. We also surveyed all UK Clinical Trials Units to identify further studies.

SELECTION CRITERIA

We included eligible retention trials of randomised or quasi-randomised evaluations of strategies to increase retention that were embedded in 'host' randomised trials from all disease areas and healthcare settings. We excluded studies aiming to increase treatment compliance.

DATA COLLECTION AND ANALYSIS

We contacted authors to supplement or confirm data that we had extracted. For retention trials, we recorded data on the method of randomisation, type of strategy evaluated, comparator, primary outcome, planned sample size, numbers randomised and numbers retained. We used risk ratios (RR) to evaluate the effectiveness of the addition of strategies to improve retention. We assessed heterogeneity between trials using the Chi(2) and I(2) statistics. For main trials that hosted retention trials, we extracted data on disease area, intervention, population, healthcare setting, sequence generation and allocation concealment.

MAIN RESULTS

We identified 38 eligible retention trials. Included trials evaluated six broad types of strategies to improve retention. These were incentives, communication strategies, new questionnaire format, participant case management, behavioural and methodological interventions. For 34 of the included trials, retention was response to postal and electronic questionnaires with or without medical test kits. For four trials, retention was the number of participants remaining in the trial. Included trials were conducted across a spectrum of disease areas, countries, healthcare and community settings. Strategies that improved trial retention were addition of monetary incentives compared with no incentive for return of trial-related postal questionnaires (RR 1.18; 95% CI 1.09 to 1.28, P value < 0.0001), addition of an offer of monetary incentive compared with no offer for return of electronic questionnaires (RR 1.25; 95% CI 1.14 to 1.38, P value < 0.00001) and an offer of a GBP20 voucher compared with GBP10 for return of postal questionnaires and biomedical test kits (RR 1.12; 95% CI 1.04 to 1.22, P value < 0.005). The evidence that shorter questionnaires are better than longer questionnaires was unclear (RR 1.04; 95% CI 1.00 to 1.08, P value = 0.07) and the evidence for questionnaires relevant to the disease/condition was also unclear (RR 1.07; 95% CI 1.01 to 1.14). Although each was based on the results of a single trial, recorded delivery of questionnaires seemed to be more effective than telephone reminders (RR 2.08; 95% CI 1.11 to 3.87, P value = 0.02) and a 'package' of postal communication strategies with reminder letters appeared to be better than standard procedures (RR 1.43; 95% CI 1.22 to 1.67, P value < 0.0001). An open trial design also appeared more effective than a blind trial design for return of questionnaires in one fracture prevention trial (RR 1.37; 95% CI 1.16 to 1.63, P value = 0.0003).There was no good evidence that the addition of a non-monetary incentive, an offer of a non-monetary incentive, 'enhanced' letters, letters delivered by priority post, additional reminders, or questionnaire question order either increased or decreased trial questionnaire response/retention. There was also no evidence that a telephone survey was either more or less effective than a monetary incentive and a questionnaire. As our analyses are based on single trials, the effect on questionnaire response of using offers of charity donations, sending reminders to trial sites and when a questionnaire is sent, may need further evaluation. Case management and behavioural strategies used for trial retention may also warrant further evaluation.

AUTHORS' CONCLUSIONS

Most of the retention trials that we identified evaluated questionnaire response. There were few evaluations of ways to improve participants returning to trial sites for trial follow-up. Monetary incentives and offers of monetary incentives increased postal and electronic questionnaire response. Some other strategies evaluated in single trials looked promising but need further evaluation. Application of the findings of this review would depend on trial setting, population, disease area, data collection and follow-up procedures.

Monitoring weight daily blocks the freshman weight gain: a model for combating the epidemic of obesity

BACKGROUND

The Tissue Monitoring System (TMS) is an algorithm that estimates changes in body tissue from a series of daily weight measures. It is intended to provide people with a feedback of changes in their tissue weight so they may have a basis for estimating how much they would have to change their intake or expenditure to maintain their weight at a prescribed level. We tested the effectiveness of the TMS to prevent freshmen from gaining weight during their first semester in college.

METHODS

In two similar but independent studies (Fall 2002, 2003), female freshmen college students were given analog bathroom scales and instructed to weigh themselves each morning immediately after rising from bed, then e-mail their weight to our staff. After 7 days, a linear function was performed on the most recent 7 days of the weight-day function for each participant. In the first study, the slope of this function was e-mailed back to the participants. In the second study, the difference between last point and the original weight was determined, using linear regression techniques, converted to calories, and the information was e-mailed back to the participants. Control participants in both studies were weighed at the beginning and the end of the semester.

RESULTS

The untreated controls gained 3.1+/-0.51 kg and 2.0+/-0.65 kg, respectively (P<0.01 for both studies), whereas weight gain of the experimental groups was 0.1+/-0.99 kg and -0.82+/-0.56 kg, values that were not significantly different than zero.

CONCLUSIONS

The TMS appears to be an effective technique to help female college freshmen resist gaining weight in an environment that is conducive to weight gain. These results suggest that the TMS may be a useful method to help curb the slow increase in the prevalence of overweight and obesity that is characteristic of all industrialized societies.

Dietary treatments of obesity

Dietary treatment of obesity is based on one or another of two premises: that the obese eat too much or that they eat the wrong things. The first is a tautology lacking explanatory power. The second is a meaningful and promising hypothesis but has yet to be effectively applied. At present, virtually all outpatient treatments of obesity, including behavior modification, are based on the first premise and consist of strategies for reducing the subject's caloric intake. Most such interventions produce short-term weight loss. Regain after the end of treatment remains the usual outcome. A survey of studies published in the period 1977-1986 and reporting on dietary or behavioral treatment of obesity reveals that the maximum percentage of body weight lost is, on average, 8.5 percent--no different from the value, 8.9%, in similar studies from 1966-1976, as reviewed by Wing and Jeffery. The principal determinant of success in such programs appears to be the intake weight of the subjects: the higher the intake weight, the more successful the intervention will appear to be. The goals and research methods of studies on dietary treatments for obesity are overdue for ethical as well as scientific reevaluation. The same may be said for the numerous programs providing such treatment outside the context of research.

Psychological correlates of weight fluctuation

This investigation attempted to determine psychological correlates of weight fluctuation in a sample of 497 normal weight and obese adults who were enrolled in a prospective, natural history study. Subjects were stratified by gender, obesity, and age and classified as weight maintainers, gainers, or losers based on their changes in weight over a 1-year period. Subjects were further classified as either weight fluctuators or nonfluctuators based on historical self-report. Nonfluctuators reported significantly higher general well-being, greater eating self-efficacy, and lower stress than weight fluctuators, regardless of body weight. Weight maintainers had more favorable eating self-efficacy related to negative affect than weight gainers. Results suggest that weight fluctuation is strongly associated with negative psychological attributes in both normal weight and obese individuals. Future research should focus on the assessment and treatment of weight fluctuation and on weight maintenance, irrespective of weight status.

Partner weight status and subject weight loss: implications for cost-effective programs and public health

This study examined the difference in body changes of subjects with overweight partners and those with normal weight partners. The 9 subjects with normal weight partners lost significantly more weight than the 14 subjects with overweight partners by the end of the one-year treatment program (27.9 lbs versus 20.2 lbs, respectively) and at 3-month follow-up (29.6 lbs vs. 17.3 lbs, respectively). It was also found that both overweight and normal weight partners lost weight incidental to treatment but as expected, body changes of overweight partners significantly decreased over time whereas body changes of normal weight partners did not. Overweight partners and subjects lost statistical equivalent amounts of weight but there was a significant correlation at posttreatment between body changes of subjects in the overweight partner group and their partners. It was concluded that if body changes of both subjects and their overweight partners are considered, couples programs might be a cost-effective and important public health approach because two individuals lose weight as inexpensively as one and more people are treated. Researchers are encouraged to report weight status and body changes of both subjects and partners in order to understand more fully the relationship between partner weight status and subject weight loss.

Shifting gears: self-reported attitudes and behaviors during times of weight loss, maintenance, and gain

One hundred and eleven respondents who had achieved at least a 15-pound (6.80 kg) weight loss in a 20-week cognitive-behavioral treatment program for obesity were asked 6 to 10 years after treatment to describe their current use of cognitive and behavioral activities during periods of weight maintenance, loss, and gain. Eleven scales were constructed to measure the self-reported frequency with which the cognitive and behavioral efforts were extended for Weight Monitoring; Food Record Monitoring; Calorie Counting; Shopping; Food Storage and Preparation; Meal Times; Snack Times; Social Occasions; Taste and Satisfaction; Physical Activity; and Sports/Exercise. A multivariate repeated-analysis of variance indicated that the respondents increased the mean frequencies with which all 11 of the cognitive and behavioral efforts were used during times of weight loss; these mean frequencies decreased during times of maintenance and decreased still further during times of weight gain. The conclusion was drawn that the respondents were able to differentiate among the types of attitudes and behaviors that they used during times of gain, maintenance, and loss.

Patterns of weight change: the interval 6 to 10 years after initial weight loss in a cognitive-behavioral treatment program

29 men and 82 women who had achieved at least a 15-lb. weight loss in a 20-wk. cognitive-behavioral treatment program for obesity were asked 6 to 10 yr. after treatment about their current weights and January 1 weights for the past five years. Four types of weight change indices were then developed to ascertain whether or not the patients had maintained their postprogram weight losses since leaving treatment. Comparisons of pre- and postprogram mean weight differences indicated that the patients had gained an average of 7.15 lb. (3.24 kg) by 1983, but there had not been a mean increase in weight since an earlier follow-up in 1978. Importantly, 32.4% reported 1983 weights below their postprogram weights, and there were no mean differences between the sexes with respect to weight changes for either 1978 or 1983. A weight index based upon percentages of weight gain since leaving treatment indicated that 40.5% had gained back more than 67% of weight that they had lost during treatment. Inspection of 90 patients' weight fluctuations over the past five years above or below their postprogram weights showed 25 distinct patterns. Each of the four weight-change indices gave different perspectives about the patients' abilities to manage their weights over time. The complexity of employing different weight-change indices for evaluating the long-term efficacy of cognitive-behavioral treatment programs for obesity was discussed.

Weight control in adolescent girls: a comparison of the effectiveness of three approaches to follow-up

The purpose of the project was to compare the effectiveness of three different types of follow-up of a weight control program in assisting adolescent girls to achieve and maintain ideal body weight. During the initial phase of the weight control program, subjects attended two sessions of approximately one hour each for eight weeks. One session each week included theory and practice of physical exercise. The other session was devoted to behavioral control of eating and diet therapy. After eight weeks, 18 subjects were divided randomly into three groups for follow-up: Group 1--monthly measurements and reinforcement of behavioral, diet, and exercise components of the weight control program; Group 2--monthly measurements; and Group 3--annual measurements. Fifteen subjects completed the 12-month follow-up program. Mean weight loss during follow-up of Group 1 was 3.65 kg, Group 2 was 1.90 kg, while Group 3 had a mean weight gain of 3.44 kg. The results suggest that regular follow-up may be a critical element in successful weight control programs for adolescent girls.

Social support and compliance: a selective review and critique of treatment integrity and outcome measurement

The paper presents a selective review and critique of the literature on social support as a factor in the enhancement of patient compliance with medical regimens. The review highlights several studies that measure the correlation between social support and compliance. The manner in which studies operationalize social support is discussed. Several research recommendations suggest ways social support could be studied as a clear and strong independent variable, such as utilizing measures of compliance with the social support manipulation and considering several different variates of social support. Greater attention to methods for measuring compliance is also suggested.

Limitations of behavioral treatment of obesity: review and analysis

Over 200 articles have been published describing behavior modification programs for weight reduction. We reviewed the group studies that reported weight data at least 1 year posttreatment. Evaluating these studies, we concluded that although changes in weight do occur, these changes are almost always clinically small, variability among patients is large, and further weight losses do not occur following the end of formal treatment. The weight lost during treatment may be explained by changes in specific eating behaviors caused by therapist contact rather than the effect of self-applied behavioral techniques on eating. Support for the effectiveness of each of the specific techniques to produce lasting weight loss or behavioral change was also lacking. Suggestions for future research in this area are given.