Study design
Full details of the study design have been published elsewhere [24, 25]. A sample of 250 study participants was determined to yield 90% power (α = .05, two-tailed) to detect a moderate effect (f = .30) for the primary dependent variables of dietary and physical activity outcomes, allowing for 20% attrition. A total of 279 postmenopausal women with type 2 diabetes, who were patients of participating primary care clinics, were recruited for the study. Inclusion criteria were: having type 2 diabetes for at least 6 months, being postmenopausal, living independently, having a telephone, ability to read English, not being developmentally disabled, and living within 30 miles of the intervention site (Eugene, OR, USA). Exclusion criteria included being older than 75 years of age or planning to move from the area within the study's time span. All patients meeting eligibility criteria were sent letters from their primary care providers, followed by phone calls inviting them to participate. Fifty-one percent of eligible women contacted agreed to participate in the study. Enrollees were representative of patients in participating primary care offices and the diabetes population of the state. A detailed description of the recruitment procedures, the adoption of the program by physicians, and its reach among patients is presented elsewhere [26]. Participants were stratified prior to randomization on physician practice, smoking status, and type of diabetes medication.
The research protocol was approved by the Oregon Research Institute Institutional Review Board (FWA 00005934), and written informed consent was obtained from all study participants prior to participation. All activities involving human subjects were in accordance with the Declaration of Helsinki, the Belmont Report, and U.S. regulations governing the protection of human research subjects. The study participants received no monetary compensation for completing assessments.
Intervention
MLP condition
The conceptual basis for this program, detailed in a previous publication [27], combined Social Cognitive Theory [28], Goal Systems [29], and Social Ecological Theory [30]. This model has evolved to include multiple system and social-environmental factors, including social support, that influence self-management of chronic illness [30]. Participants were able to set personal lifestyle change goals at the start of the intervention, and then received ongoing peer and professional support for their goals throughout the treatment program.
The MLP was delivered by a registered dietitian, an exercise physiologist, a stress-management instructor, and a combination of professional and lay support group leaders. The program started with a 2 1/2-day non-residential retreat, which was followed by 4-hour weekly meetings consisting of 1 hour each of Mediterranean-style potluck, physical activity, stress management, and support groups. The intervention was conducted in four sequential waves, 2 months apart, with approximately 40 treatment condition and 30 control condition participants in each wave. This schedule was necessary to keep the group size manageable within staff and space constraints.
The first 6 months of the intervention were designed to teach the program components and build group cohesion.
Mediterranean diet
The project registered dietitian taught participants the Mediterranean alpha-linolenic acid-rich diet, which is low in saturated fat but moderately high in more healthful monounsaturated fats [31]. Individualized carbohydrate and fat recommendations were provided to optimize blood glucose and lipid concentrations. The Mediterranean diet recommended more bread; more root vegetables, green vegetables, and legumes; more fish; less red meat (e.g., beef, lamb, pork), replaced by poultry; daily fruit; and avoidance of butter and cream, to be replaced by olive/canola oil or olive/canola-based margarine. MLP participants were asked to complete and bring to some weekly meetings a simple self-monitoring log of their adherence to the Mediterranean diet components.
Physical activity
The initial physical activity goal, developed in consultation with the project's exercise physiologist, was consistent with the recent Centers for Disease Control and Prevention and the American College of Sports Medicine guidelines for physical activity [32]: 30 minutes of moderate physical activity on most days of the week. Once that goal was achieved, participants were advised to build up to 1 hour of moderate aerobic activity daily. Women who had engaged in little or no activity before the program were helped to set individualized goals to gradually increase activity, by adding about 5 minutes per session or more days per week of exercise.
Stress management
Using procedures from Ornish [21] and Toobert et al. [23], participants were instructed in yoga, progressive deep relaxation, meditation, and directed or receptive imagery. The purpose of each technique was to increase the sense of relaxation, concentration, and awareness. Participants were asked to practice all of these techniques for at least 1 hour per day and received a videotape to assist them.
A variety of motivational techniques were employed to keep the meetings interesting and to boost attendance, including contests, self-monitoring, and group and individual rewards.
After 6 months of intervention, MLP participants were further randomized to one of two maintenance conditions: (1) a faded schedule of weekly meetings led by lay leaders or (2) four meetings over 18 months with project staff to complete a personalized, computer-assisted program. This personalized support condition was designed to enhance use of social and environmental resources for healthful lifestyle changes. An interactive computer-based program was developed to assess an individual's use of available supportive resources, and to help users set goals for taking better advantage of these resources. These two maintenance conditions were set up to test whether targeted, computer-assisted enhancement of social support promoted better maintenance of initial gains than continued group weekly meetings. The two maintenance conditions were compared separately to the control condition at 12 and 24 months. With about 80 study participants in each maintenance condition and 116 in the control group, sufficient power existed to detect an effect size of f = .30.
Usual care control condition
Participants in the control condition completed all assessment procedures. These participants received no additional intervention beyond usual care from their physicians.
Measures
Women were assessed in groups of 6–8 at Oregon Research Institute in Eugene, OR. Some demographic measures were collected on the telephone for screening purposes prior to randomization; all other measures were collected at baseline prior to randomization and at 6, 12, and 24 months following introduction of the lifestyle program.
To ensure adherence to the assessment schedule, a variety of techniques were used. Ten days prior to the assessment, participants were mailed pre-visit packets which included a reminder letter with the date of their visit, a description of the assessment and what to bring, and two surveys to complete. Transportation needs were met by the project, if necessary, usually by providing a taxi and occasionally by arranging carpooling. Though rare, child care and/or elder care costs also were covered when requested. Assessments were scheduled so that friends could attend the same session. The assessors created a welcoming environment so that many participants looked forward to their assessment visits. Also used to boost assessment participation were telephone reminders, holiday and birthday cards, continued address updates, and flexibility (a 3-month window) in the time frame for assessment completion.
A relatively large number of measures was required because of the many anticipated effects of the multiple-risk-factor intervention, the need to measure each of the multiple behavioral targets, and the lack of gold standards for measuring most of the behaviors. Multivariate analyses of variance were used to limit experiment-wide error and to provide a stronger, more robust approach than the arbitrary selection of one behavioral or process measure.
Behavioral outcomes
Dietary
The semi-quantitative food frequency questionnaire (FFQ) developed at the Fred Hutchinson Cancer Research Center [33] was used to document percent of calories from saturated fat. This FFQ has been validated with 4-day food records and 24-hour dietary recalls (average correlation r = .5). The validity of the percent of dietary saturated fat measured by the FFQ was assessed in this study by saturated fatty acids from a plasma fatty acid profile. Using the control group only, the 24-month correlation between intake of saturated fat measured by the FFQ and plasma concentrations of saturated fatty acids was r = .26, p < .01.
Physical activity
The CHAMPS Activities Questionnaire for Older Adults [34] provided an estimate of kilocalories/kilogram/hour of moderate-intensity exercise-related activities, which incorporates the three key components of physical activity: frequency, duration, and intensity. The CHAMPS is a widely used measure that has been shown to be sensitive to change in similar populations. Women also were monitored for 7 days with the Yamax DW-500 pedometer to record the number of steps taken daily. Pearson product-moment correlation coefficients between the CHAMPS scale and the pedometer recordings were averaged for the four study time points, yielding a moderate but significant result (r = .28, p < .001).
Stress management
Since objective measures of stress-management practices are not well-established, a self-monitoring form was designed for this study (Figure 1). Participants monitored their daily performance of at least 20 minutes of yoga stretches, 5 minutes of breathing exercises, 15 minutes of progressive relaxation, and 5 minutes each of meditation and visualization. Each scale consisted of the number of self-monitored minutes of stretching, breathing, or meditation/visualization for each of 7 days. Each of the three subscales was made up of 7 items or days. Trunk flexion and shoulder range-of-motion tests were conducted to assess changes in flexibility resulting from the yoga practices.
Social desirability
To evaluate and adjust for the relations between social desirability and the behavioral and psychosocial measures, the Balanced Inventory of Desirable Responding [35] was used. Paulhus [36] reported a coefficient alpha of .83 for the all items, and test-retest correlations of between .65 and .69.
Psychosocial measures
Social resources
Since the MLP intervention targeted different sources of support (e.g., friends, family, health care providers), measures were included to address each of these components. The Brief Chronic Illness Resources Survey (CIRS) [30] provided a profile of an individual's support for behavior-specific disease management, ranging from more proximal support (e.g., family and friends) to more distal factors (e.g., neighbourhood or community). In these analyses, the total score from the CIRS was used to represent received support. The UCLA [37] measures three types of support (i.e., informational, tangible, emotional), three dimensions of support (i.e., amount, satisfaction, reciprocity), and four sources of support (i.e., friends, relatives, partner, organizations). For this project, two other sources of support – people in a support group and medical care providers – were added to the original UCLA. The Total Positive and Total Negative scales were included in these analyses.
Problem-solving ability
The Diabetes Problem-Solving Interview was developed for adults with type 2 diabetes [38]. For this study, the interview was modified to ask respondents to write a description of how they would react to nine scenarios presenting potential challenges to program adherence. Coders scored responses to produce an average rating of problem-solving skill. Inter-rater reliability on these scores ranged from r = .57 to r = .90 and averaged r = .72. Six-month test-retest reliabilities using only the control group was r = .51 for overall skill ratings.
Self-efficacy
Two measures of self-efficacy were used to assess different areas of diet and physical activity-related obstacles. Confidence in Overcoming Challenges to Self-Care was used to assess confidence overcoming obstacles to adhering to diet, physical activity, and stress-management [39]. This 49-item instrument assesses confidence in overcoming such factors as cost, time, social pressures, competing demands, and thoughts associated with achieving one's dietary, physical activity, and stress-management goals. Recent analyses of this instrument [39] demonstrated reasonable psychometric properties for a brief scale (test-retest reliability r = .60; internal consistency (α = .50). The total score was used in these analyses. Participants' self-efficacy for achieving their dietary and physical activity goals was assessed using the Sallis Self-Efficacy for Diet and Exercise Behavior instrument [40]. This instrument assesses confidence in performing diet and exercise behaviors for at least 6 months. The Eating Behavior scale contains 20 items (test-retest reliability ranged from r = .43 to .64; Cronbach's α .84) and the Self-Efficacy for Exercise scale contains 12 items (test-retest reliability was r = .68; α coefficients ranged from .85 to .93) [40].
Depression
Since CHD and diabetes are closely linked to depression [13]., the Center for Epidemiologic Studies Depression Scale (CES-D) was administered. The CES-D is a general measure of depressive symptoms that has been shown to have good reliability and validity [41], and has been used extensively in epidemiologic studies.
Perceived stress
The Perceived Stress Scale was administered to determine whether perceived stress changed in conjunction with the stress-management intervention. This 14-item measure, based on the transactional stress theory of Lazarus, has been found to be an independent and significant predictor of physical symptoms and health behaviors after controlling for psychological symptoms [42].
Quality of life
The Diabetes Distress Scale (DDS), a diabetes-specific measure of quality of life, also was used. Respondents rated the degree to which common barriers to adherence were problematic for them (lower ratings indicate better perception of quality of life). This scale assessed diabetes-specific overall emotional distress, interpersonal distress, regimen-related distress, and physician-related distress. A recent 32-item revision of the DDS [43] produces subscales on these four dimensions as well as an overall score; lower scores indicate better quality of life. The DDS has good internal reliability with the four subscales (α = 0.87), and has been shown to be responsive to psychosocial intervention [43]. Two of the four DDS scales were used: the regimen-related and interpersonal distress scales.
Cost analysis
Using methods described in detail elsewhere [44], an economic analysis of the costs associated with the MLP intervention was conducted. The analysis was conducted primarily from the perspective of the potential adopting organization or potential payer, such as Medicare or a health insurance plan. The analysis evaluated the cost of delivering the MLP compared to the UC condition. Using retrospective data collected during the development and implementation of the MLP, estimates were made of total intervention costs, incremental costs associated with the intervention group relative to the comparison condition, costs per participant, and marginal costs per incremental improvement in several of the primary outcomes. Total intervention costs were estimated as the sum of the costs associated with recruitment of participants (in the intervention arm) and staff; labor costs associated with the time spent by educators, dietitians, physicians, exercise physiologists, meeting leaders, and support group leaders; retreats; training, phone charges, and supplies; and rent attributable to facility space needed for group meetings. All assessment costs were excluded.
Statistical methods
Descriptive analyses, including means, standard deviations, and distributions, were used to clean the data, determine whether transformations were needed, and describe overall level of improvement and implementation. One-way analyses of variance (ANOVA) were used to evaluate between-condition differences at baseline. Repeated measures multivariate analyses of covariance (MANCOVA), covarying out the effect of baseline scores, were used to compare long-term results on each of the three sets of outcome measures at 6, 12, and 24 months across conditions. Follow-up univariate analyses of covariance (ANCOVA) were conducted to reveal the source of effects only when the MANCOVA was significant in a given domain. To aid interpretation, the results reported in all tables have not been adjusted for baseline values.
Additional covariates
Prior to conducting the repeated measures MANCOVAs, univariate statistics and correlation matrices were examined for potential additional correlates of the behavioral and psychosocial dependent variables. For the behavioral outcomes, social desirability, income, number of comorbid conditions, and age were all entered as covariates, and none was a significant contributor to the models. Social desirability was entered as a covariate in all of the psychosocial analyses presented.
Missing data
All analyses were performed two ways. First, a complete-case approach was used. Participants with missing follow-up data on the outcome variable of interest were excluded from the analysis. Second, identical analyses were conducted after missing data were imputed using EMCOV [45]. Significance and conclusions from imputed analyses were mostly identical or stronger compared to complete-case analyses. For ease of understanding, the nonimputed results are presented in the tables, with the imputed results, where different, described in the text.
