Statistical analysis of randomized trials in tobacco treatment: longitudinal designs with dichotomous outcome.

This article considers two important issues in the statistical treatment of data from tobacco-treatment clinical trials: (1) data analysis strategies for longitudinal studies and (2) treatment of missing data. With respect to data analysis strategies, methods are classified as 'time-naïve' or longitudinal. Time-naïve methods include tests of proportions and logistic regression. Longitudinal methods include Generalized Estimating Equations and Generalized Linear Mixed Models. It is concluded that, despite some advantages accruing to 'time-naïve' methods, in most situations, longitudinal methods are preferable. Longitudinal methods allow direct effects of the tests of time and the interaction of treatment with time, and allow model estimates based on all available data. The discussion of missing data strategies examines problems accruing to complete-case analysis, last observation carried forward, mean substitution approaches, and coding participants with missing data as using tobacco. Distinctions between different cases of missing data are reviewed. It is concluded that optimal missing data analysis strategies include a careful description of reasons for data being missing, along with use of either pattern mixture or selection modeling. A standardized method for reporting missing data is proposed. Reference and software programs for both data analysis strategies and handling of missing data are presented.

A randomized trial to reduce passive smoke exposure in low-income households with young children.

OBJECTIVE: Passive smoke exposure among children is widespread in the United States; estimates suggest that almost 40% of children who are younger than 5 years live with a smoker. Few randomized studies of passive smoke exposure reduction among children have been conducted, and the impact of interventions that have been evaluated has been limited. The objective of this study was to determine whether a motivational intervention for smoking parents of young children will lead to reduced household passive smoke exposure. METHODS: Project KISS (Keeping Infants Safe From Smoke), a theory-driven exposure reduction intervention targeting low-income families with young children, was a randomized controlled study in which participants-smoking parents/caregivers (N = 291) who had children who were younger than 3 years and who were recruited through primary care settings-were randomly assigned to either the motivational intervention (MI) or a self-help (SH) comparison condition was used. Follow-up assessments were conducted at 3 and 6 months. The MI condition consisted of a 30- to 45-minute motivational interviewing session at the participant's home with a trained health educator and 4 follow-up telephone counseling calls. Feedback from baseline household air nicotine assessments and assessment of the participant's carbon monoxide level was provided as part of the intervention. Participants in the SH group received a copy of the smoking cessation manual, the passive smoke reduction tip sheet, and the resource guide in the mail. Household nicotine levels were measured by a passive diffusion monitor. RESULTS: The 6-month nicotine levels were significantly lower in MI households. Repeated measures analysis of variance across baseline, 3-month, and 6-month time points showed a significant time-by-treatment interaction, whereby nicotine levels for the MI group decreased significantly and nicotine levels for the SH group increased but were not significantly different from baseline. CONCLUSIONS: This study targeted a large sample of racially and ethnically diverse low-income families, in whom both exposure and disease burden is likely to be significant. This is the first study to our knowledge that has been effective in reducing objective measures of passive smoke exposure in households with healthy children. These findings have important implications for pediatric health care providers, who play an important role in working with parents to protect children's health. Providers can help parents work toward reducing household passive smoke exposure using motivational strategies and providing a menu of approaches regardless of whether the parents are ready to quit.

Stage of change, decisional balance, and temptations for smoking: measurement and validation in a large, school-based population of adolescents.

Developing interventions for reducing adolescent smoking rates based on the Transtheoretical Model (TTM) requires the development of quality measures of the key constructs of the model. The goal of this investigation was to evaluate the psychometric properties of measures of Stage of Change, Decisional Balance and Situational Temptation for both smokers and nonsmokers and to test if the predicted relationships between these constructs were confirmed in a large (N=2808) sample of adolescents. A correlated three factor model (Social Pros, Coping Pros and Cons) provided an excellent fit to the 12-item Decisional Balance inventory for both smokers (CFI=0.957) and nonsmokers (CFI=0.963). A hierarchical four factor model (negative affect, positive social, habit strength and weight control) provided an excellent fit to the eight-item Situational Temptations inventory for smokers (CFI=0.969). A hierarchical five-factor model (same four as smokers plus Curiosity) provided an excellent fit to the 10-item Situational Temptations inventory for nonsmokers (CFI=0.943). The relationships between both the Decisional Balance and temptation scales and the Stages of Change were verified for both smokers and nonsmokers. The measures for adolescents are similar to but not the same as the measures of these constructs for adults.

Evaluating a population-based recruitment approach and a stage-based expert system intervention for smoking cessation.

A stage-matched expert system intervention was evaluated on 4144 smokers in a two-arm randomized control trial with four follow-ups over 24 months. Smokers were recruited by random digit-dial calls, and 80.0% of the eligible smokers were enrolled. Individualized and interactive expert system computer reports were sent at 0, 3, and 6 months. The reports provided feedback on 15 variables relevant for progressing through the stages. The primary outcomes were point prevalence and prolonged abstinence rates. At 24 months, the expert system resulted in 25.6% point prevalence and 12% prolonged abstinence, which were 30% and 56% greater than the control condition. Abstinence rates at each 6-month follow-up were significantly greater in the Expert System (ES) condition than in the comparison condition with the absolute difference increasing at each follow-up. A proactive home-based stage-matched expert system smoking cessation program can produce both high participation rates and relatively high abstinence rates.

Intervention and policy issues related to children's exposure to environmental tobacco smoke.

BACKGROUND: Children's exposure to environmental tobacco smoke (ETS) is unacceptably high; almost 40% of children in the United States are regularly exposed to ETS. METHODS: This paper presents a review of the literature that evaluates interventions designed to reduce ETS exposure among young children. In addition, it presents the study design for Project KISS (Keeping Infants Safe from Smoke), an intervention designed to utilize exposure-related feedback to increase parents' motivation for ETS reduction and to reduce household ETS levels. Baseline data are presented to illustrate factors that should be addressed in ETS interventions. RESULTS: The literature review demonstrates the dearth of studies in the literature targeting ETS reduction among children. Participants in Project KISS believed that smoking had affected their children's health and were in later stages of motivational readiness to quit smoking than is typically observed. However, they face a number of challenges to smoking, such as high prevalence of nicotine dependence, high prevalence of living with other smokers, and socioeconomic and stress-related barriers. CONCLUSIONS: The policy implications of this research are discussed, and recommendations are made for future research.

Counselor and stimulus control enhancements of a stage-matched expert system intervention for smokers in a managed care setting.

BACKGROUND: Previous research has demonstrated the efficacy of an interactive expert system intervention for smoking cessation for a general population. The intervention provides individualized feedback that guides participants through the stages of change for cessation. Enhancing the expert system by adding proactive telephone counseling or a stimulus control computer designed to produce nicotine fading could produce preventive programs with greater population impacts. METHODS: Four interventions were compared: (a) the interactive expert system intervention; (b) the expert system intervention plus counselor calls; (c) the expert system intervention plus the stimulus control computer; and (d) an assessment only condition. A 4 (intervention) x 4 (occasions) (0,6,12, and 18 months) design was used. Smokers were contacted at home via telephone or mail. The initial subject pool was the 24,178 members of a managed care company. Screening was completed for 19,236 members (79.6%), of whom 4,653 were smokers; 85.3% of the smokers were enrolled. RESULTS: Thirty-eight percent were in the precontemplation stage, 45% in the contemplation stage, and only 17% in the preparation stage. At 18 months, the expert system resulted in 23.2% point prevalence abstinence, which was 33% greater than that of assessment only. The counselor enhancement produced increased cessation at 12 months but not at 18 months. The stimulus control computer produced no improvement, resulting in 20% worse cessation rates than the assessment only condition. CONCLUSIONS: The enhanced conditions failed to outperform the expert system alone. The study also demonstrated the ability of the interactive expert system to produce significantly greater cessation in a population of smokers than assessment alone.

Validation of decisional balance and situational temptations measures for dietary fat reduction in a large school-based population of adolescents.

Brief, validated, and reliable theory-based measures specifically designed for use in large survey research with adolescent populations are needed to assess attitudes and behaviors about dietary fat consumption. This study validated two transtheoretical model (TTM)-based instruments in 2639 ninth graders from 12 Rhode Island high schools. The Decisional Balance Questionnaire for Adolescent Dietary Fat Reduction (DBQA) measures the importance adolescents assign to the pros and cons of reducing dietary fat consumption, while the Situational Temptations Questionnaire for Adolescents (STQA) measures temptations to eat high-fat foods as both a global construct and across three categories of challenging situations. Four competing models were compared for each instrument. An eight-item, correlated two-factor Pros and Cons model was validated for the decisional balance measure and a nine-item, three-factor hierarchical model was validated for situational temptations. The theoretically predicted relationships between stage of change and the pros and cons, as well as stage and situational temptations were supported. These results demonstrate that both measures have sound psychometric properties and are externally valid.

Cluster subtypes within stage of change in a representative sample of smokers.

In this paper a three-level conceptualization of approaches to matching self-help behavior change strategies to individuals is presented based on the Transtheoretical Model of Change. Two of the model's intervention approaches, tailoring to Stage-of-Change and creating completely individualized interventions, have already been developed and implemented in previous research. A third intervention approach, in between stage-tailored and individualized, is targeting subtype groups within each Stage of Change. The subtype targeted intervention approach is in the initial development stage of empirically determining and validating the stage subtypes. Three studies are presented which investigate stage subtypes within a representative sample of 4,144 smokers in the Precontemplation, Contemplation, and Preparation Stages of Change. Within each Stage-of-Change study, two cluster analyses were performed using the Pros, Cons, and Situational Temptations from the Transtheoretical Model to establish cluster replicability. Cluster solutions were externally validated using the 10 Processes of Change and 2 smoking behavior variables. Four distinct subtypes were found in Precontemplation and Contemplation, and five subtypes were found in Preparation. These subtypes closely replicate subtypes previously found in a convenience sample of smokers and provide strong evidence for the existence of subtypes within the first three Stages of Change.

Stages of change across ten health risk behaviors for older adults.

Owing to the recent success of the Transtheoretical Model of behavior change and the possible relationships between health behaviors, this study investigated the stage distribution of 10 healthy behaviors (seatbelt use, avoidance of high fat food, eating a high-fiber diet, attempting to lose weight, exercising regularly, avoiding sun exposure, sunscreen use, attempting to reduce stress, stopping smoking, and conducting cancer self-exams) and their interrelationships in a representative sample of health maintenance organization (HMO) members. The majority of older adults were found to be in either precontemplation or maintenance, illustrating the need to target interventions to precontemplation. Most older individuals were in precontemplation for losing weight and/ or sunscreen use and exercise, making these behaviors a priority for intervention research. Possible gateway behaviors to general health could be identified; however, these results are preliminary and require longitudinal follow-up.

Decisional balance for immoderate drinking in college students.

Immoderate drinking in college is common and is associated with significant negative sequelae. In this study, measures of Decisional Balance for Immoderate Drinking were developed. This construct is proposed to represent the basic decision-making process that is used by students when deciding whether to drink at immoderate levels or not. Furthermore this construct is embedded in a larger model of behavior change, the Transtheoretical Model of Change, which has been shown to be effective in understanding many health-related behaviors across a wide variety of populations. A total of 629 college students were administered a 25-item decisional balance questionnaire in 1993-1994. Exploratory and confirmatory analyses suggested two different solutions, a two-factor solution and a three-factor solution, but did not provide clear evidence for the psychometric superiority of one over the other. The three-factor solution was chosen as it was seen as an elaboration of the two-factor solution, and validity evidence for this solution is presented. The three factors were labeled the Pros, the Cons-Actual, and the Cons-Potential of Immoderate Drinking. The Cons-Actual scale is a measure of negative affective states associated with current drinking whereas the Cons Potential measures the risk of more concrete negative effects of drinking. External validity was established by the significant and meaningful differences on a number of alcohol-related variables including consumption variables, three measures of negative sequelae of immoderate drinking, and Stage of Change, the organizing construct of the Transtheoretical Model of Change.

Testing 40 predictions from the transtheoretical model.

Sensitive measurement of behavior change requires dependent measures that are sensitive to the whole spectrum of change, not just a single aspect of change. Traditional outcome variables such as point prevalence for smoking cessation focus on a single discrete event and ignore all other progress. Alternatively, the criterion measurement model (CMM) is an approach that posits a three-construct outcome model (habit strength, positive evaluation strength, and negative evaluation strength), where different constructs are sensitive to change for different aspects of the temporal domain. In this article, a series of 40 differential a priori predictions were tested using a large representative sample of smokers. The focus was on the prediction of specific effect sizes rather than statistical significance. A series of comparisons involving stage transitions was examined using five variables representing the three CMM constructs. The predictions involved movement from one of three initial stages (precontemplation, contemplation, and preparation) to stage membership 12 months later. Thirty-six of the 40 predictions were confirmed, indicating that the outcome model has strong construct validity and accurately reflects movement between the stages of change.

An expert system intervention for smoking cessation.

The Pathways to Change system (PTC) is an expert system intervention for smoking cessation. Assessments are performed either by mail or by a telephone interview and each smoker receives a three- to four-page report that provides individualized recommendations matched to the individual's needs and readiness-to-change. The Transtheoretical Model of Change provides the theoretical basis for the expert system. Four different studies have demonstrated the efficacy of this intervention in a general population, with cessation rates of 22 to 26%. Furthermore, the difference between the groups was larger at each follow-up assessment point, indicating that the effects of the treatment increased long after the end of treatment. The studies involved two proactively recruited samples, demonstrating that a large proportion (85.3% and 82.5%) of the population of smokers could be successfully recruited into a smoking cessation program. Expert system interventions have the potential to have an extremely high impact on a total population of smokers.

Stage of regular exercise and health-related quality of life.

BACKGROUND: Research on cognitive factors and motivational readiness for exercise is important for increasing our understanding of behavior change among those with sedentary lifestyles. This study examines stage of change for regular exercise and self-perceived quality of life. METHODS: Data are from 1,387 respondents to a random digit dial survey of health behaviors. Stage of change is assessed with a single item, and individuals are classified with respect to intention and exercise behavior. Quality of life is assessed with the SF-36, a multidimensional measure of health-related quality of life. RESULTS: Exercise stage is associated with self-perceived quality of life. The three areas most strongly related were physical functioning, general health perceptions, and vitality. Physical functioning scores were lowest in precontemplation and highest in maintenance. Vitality and mental health scales were related to exercise behavior, but not to intention. CONCLUSIONS: Cognitions about self-perceived quality of life vary across the stages of change, with those who are least prepared to adopt regular exercise reporting the lowest levels of quality of life. These findings suggest that cognitive-motivational messages designed to emphasize quality of life benefits associated with exercise may be useful intervention strategies for people who are less motivationally ready to change.

Stage distributions for five health behaviors in the United States and Australia.

BACKGROUND: A key variable for the design of individual and public health interventions is the Stage of Change. The five stages of readiness to change are Precontemplation, Contemplation, Preparation, Action, and Maintenance. The distribution of individuals across the stages of change can provide a valuable tool for designing health interventions. METHODS: The pattern of distribution across the stages of change for five behavioral risk factors is presented from five independent surveys, two from the United States and three from Australia. The five risk factors are smoking, low fat diet, regular exercise, reducing stress, and losing weight. Identical single-item questionnaire items for staging health behaviors were used in all surveys. RESULTS: The stage distributions for the five risk factors were similar across the five independent samples. In general, the pattern of stage distributions was stable across health risk factors, gender, country, and sample. CONCLUSIONS: Single-item survey measures of stage of change that are readily applicable to population studies appear to provide important information about the population characteristics of readiness to change behavioral risk factors. The stability of these distributions suggests that interventions matched by stage may have broad applicability.

Interactive versus noninteractive interventions and dose-response relationships for stage-matched smoking cessation programs in a managed care setting.

This study compared interactive and noninteractive smoking cessation interventions for a population of smokers who were all members of 1 division of a managed care company. In addition, it examined whether a dose-response relationship existed. Screening was completed for 19,236 members who were contacted by telephone or mail. Of the 4,653 who were identified as smokers, 85.3% were enrolled. A 2 Intervention (interactive or noninteractive) x 4 Contacts (1, 2, 3, or 6 contacts) x 4 Occasions (0, 6, 12, and 18 months) design was used. The interactive intervention was stage-matched expert-system reports plus manuals; the noninteractive intervention was stage-matched manuals. Contact occurred in 1 of 4 series (1, 2, 3 or 6 contacts) at 3-month intervals. The expert system outperformed the stage-matched manuals, but there was no clear dose-response relationship for either intervention.

Increasing mammography among women aged 40-74 by use of a stage-matched, tailored intervention.

BACKGROUND: Tailoring is a promising technique for encouraging greater performance of health-related behaviors. Tailored interventions are designed to be more individualized to personal characteristics, in contrast to "standard" interventions where all participants receive the same materials. METHODS: A total of N = 1864 women aged 40-74 were recruited from a staff model HMO and randomly assigned to one of three intervention groups: (a) No Educational Materials, (b) Standard Materials, and (c) Stage-Matched Materials. A provider-directed component was common across all three conditions. The Standard and Stage-Matched groups each received two mailed educational packets after baseline and follow-up telephone interviews. The Stage-Matched intervention was based on the Transtheoretical Model of behavior change. RESULTS: Analyses of n = 1397 women (after all attrition) showed that receipt of mammography after the baseline interview was higher for the Stage-Matched group (63.6%) than for the No Materials group (54.9%; OR = 1.43, 95% CI = 1.10, 1.86). The Standard intervention group was intermediate (58. 5%). The Standard group did not differ from the No Materials group, but did differ from the Stage-Matched group in multivariate analysis. CONCLUSIONS: Stage-matched, tailored materials may be a means to encourage screening mammography. Such interventions can be implemented by telephone and mail.

Measuring support for tobacco control policy in selected areas of six countries.

OBJECTIVE: To explore the validity, reliability, and applicability of using a short, psychometrically sound survey instrument to measure population attitudes toward tobacco control policies. DESIGN: Surveys. SUBJECTS AND SETTING: Student respondents attending university in Australia (n = 403), Hong Kong (n = 336), the Netherlands (n = 351), South Africa (n = 291), the United Kingdom (n = 164) and the United States (n = 241); total n = 1786. MAIN OUTCOME MEASURE: The Smoking Policy Inventory (SPI), a 35-item scale. SPI scores were adjusted for age, income, gender, and smoking status. Estimates of internal consistency and tests of factorial invariance were conducted in each sample. RESULTS: Across all six countries, the SPI was found to be highly reliable and to have a consistent factor structure, indicating that the SPI scale represents a higher order construct that assesses general attitudes about tobacco control policy with five dimensions. In general, the degree of endorsement of anti-tobacco policies as measured by the SPI reflected the extent and strength of tobacco control legislation in those countries. Dutch students were the least likely, and Australian and Hong Kong students the most likely, to support tobacco control policies. CONCLUSIONS: It is possible to develop appropriate and meaningful measurement tools for assessing support of tobacco control policies. Strong evidence was found for internal reliability and structural invariance of the SPI. The SPI may be a useful mechanism for monitoring ongoing policy initiatives, making cross-cultural comparisons, and evaluating population receptiveness to proposed policy approaches.

Stages of acquisition and cessation for adolescent smoking: an empirical integration.

Adolescent cigarette smoking acquisition and cessation were integrated into a single nine-stages-of-change continuum using the transtheoretical model of change framework. Findings in a high school student sample (n > 700) showed that a few of the never smokers were planning to try smoking, and half of the current smokers were contemplating quitting. More than half of former smokers were long-term quitters. The high pros of smoking scores assessing coping benefits of cigarettes were related to smoking acquisition and the high con (disadvantages) scores to long-term abstinence. Never smokers were most tempted to try smoking when they anticipated that smoking would help reduce negative and increase positive mood. Current and former smokers were tempted due to peer cigarette offers and negative mood. These temptations were significantly reduced among ex-smokers.

Time series analysis in historiometry: a comment on Simonton.

Time series analysis (TSA) is one of a number of new methods of data analysis appropriate for longitudinal data. Simonton (1998) applied TSA to an analysis of the causal relationship between two types of stress and both the physical and mental health of George III. This innovative application demonstrates both the strengths and weaknesses of time series analysis. Time series is applicable to a unique class of problems, can use information about temporal ordering to make statements about causation, and focuses on patterns of change over time, all strengths of the Simonton study. Time series analysis also suffers from a number of weaknesses, including problems with generalization from a single study, difficulty in obtaining appropriate measures, and problems with accurately identifying the correct model to represent the data. While careful attempts are made to minimize these problems, each is present in the Simonton study, although sometimes in a subtle manner. Changes in how the data could be gathered are suggested that might help to solve some of these problems in future studies. Finally, the advantages and disadvantages of employing alternative methods for analyzing multivariate time series data, including dynamic factor analysis, are discussed.