A Positive Psychology–Motivational Interviewing Intervention to Promote Positive Affect and Physical Activity in Type 2 Diabetes: The BEHOLD-8 Controlled Clinical Trial

Abstract

Objective:

Physical activity is associated with superior health outcomes in patients with type 2 diabetes (T2D), but most T2D patients do not follow physical activity recommendations. The objective of this study was to assess the feasibility and impact of a novel combined positive psychology–motivational interviewing (PP-MI) intervention to promote physical activity in T2D.

Methods:

This controlled clinical trial compared an 8-week, phone-delivered PP-MI intervention to an attention-matched MI-enhanced behavioral counseling condition among 60 participants with T2D and suboptimal moderate to vigorous physical activity (MVPA; <150 min/wk). The primary study outcome was feasibility (proportion of sessions completed) and acceptability (0–10 ease and utility ratings of each session). Secondary outcomes were between-group differences in changes in positive affect (main psychological outcome) and accelerometer-measured physical activity (MVPA and steps per day), using mixed-effects regression models, at 8 and 16 weeks.

Results:

Ninety-two percent of PP-MI sessions were completed, and mean participant ratings of ease/utility were 8.5 to 8.8/10, surpassing a priori benchmarks for feasibility and acceptability. PP-MI participants had small-medium effect size (ES) difference improvements in positive affect compared with MI (8 weeks: estimated mean difference [EMD] = 3.07 [SE = 1.41], p = .029, ES = 0.44; 16 weeks: EMD = 2.92 [SE = 1.73], p = .092, ES = 0.42). PP-MI participants also had greater improvements in MVPA (8 weeks: EMD = 13.05 min/d [SE = 5.00], p = .009, ES = 1.24; 16 weeks: EMD = 7.96 [SE = 4.53], p = .079, ES = 0.75), with similar improvements in steps per day.

Conclusions:

The PP-MI intervention was feasible and well accepted. Next-step efficacy studies can more rigorously explore the intervention’s effects on physical activity and clinical outcomes.

Trial Registration:

ClinicalTrials.gov Registration No. NCT03150199.

INTRODUCTION

Most of the 27 million Americans (1) with type 2 diabetes (T2D) are unable to follow consensus physical activity recommendations (2,3), and low physical activity is independently associated with T2D complications, cardiovascular disease development, and death (2,4). Given the growing prevalence and substantial morbidity associated with T2D (1,5), effective interventions to promote physical activity in this population are badly needed. Unfortunately, existing multicomponent physical activity interventions for T2D have been difficult to implement in clinical settings because of their intensity and complexity (6). There is a need to develop new physical activity interventions that are powerful enough to precipitate and sustain change and feasible enough to allow real-world use.

Motivational interviewing (MI) is an evidence-based, patient-centered counseling strategy that enhances intrinsic motivation for change by allowing patients to articulate their own reasons for changing (7). It requires comprehensive training and practice (8), but can be delivered remotely with good fidelity (9). MI can enhance multicomponent interventions to promote physical activity and other health behaviors (10). However, MI alone has had limited effects on physical activity in T2D (11). Complementary strategies that can boost MI’s effectiveness would therefore fill a major gap in clinical care.

Positive psychology (PP) interventions may significantly enhance the effects of physical activity programs. Baseline levels of positive psychological constructs (e.g., optimism or positive affect) have predicted greater subsequent physical activity, controlling for baseline activity, demographics, medical illness, and the adverse effects of depression (12,13). PP interventions use straightforward exercises (e.g., writing gratitude letters, recalling successes) in a systematic manner to promote these positive cognitive and emotional states (14). Such interventions require limited training and can be delivered by a variety of disciplines (15,16), improving scalability of such programs. In randomized trials, PP interventions have led to significant increases in physical activity in patients with medical illness (17). PP could therefore add an easy-to-deliver, effective component to an intervention for inactive persons who have T2D.

A combined PP-MI intervention could be a powerful approach to promoting activity in persons with T2D. The MI component provides a specific focus on motivations, barriers, and goals related to physical activity. The PP component more broadly targets psychological well-being, confidence, and optimism, which could enhance engagement in MI (18) and have direct effects on physical activity (13). A phone-delivered PP-MI program in T2D was well accepted and associated with improved physical activity in an initial proof-of-concept trial (19), but such a program had never been compared with an MI-based control condition.

Accordingly, we assessed the feasibility, acceptability, and impact of an 8-week, phone-delivered PP-MI intervention to promote activity among T2D patients who had low baseline physical activity, compared with an attention-matched MI-enhanced behavioral counseling strategy for physical activity. We hypothesized that the PP-MI intervention would meet a priori benchmarks for feasibility and acceptability and would have medium effect size (ES) improvements in positive affect (main psychological outcome) and accelerometer-measured activity, compared with the control condition.

METHODS

Overview

The Boosting Emotional well-being and Happiness in Outpatients Living with Diabetes 8-week (BEHOLD-8) trial examined the feasibility and impact of a PP-MI phone-delivered intervention compared with a time-matched MI-enhanced behavioral counseling strategy. Participants, enrolled from outpatient clinics in an urban academic medical center from June 2017 to May 2019 (follow-up complete August 2019), were primary care patients with T2D and low physical activity (Supplemental Digital Content Table 1 for CONSORT checklist, http://links.lww.com/PSYMED/A649). The study was approved by the Partners Healthcare System Institutional Review Board and was preregistered on ClinicalTrials.gov (NCT03150199). All participants provided written informed consent.

Participants

Study Criteria

To be eligible, participants were required to meet the following inclusion criteria:

1. T2D. Eligible patients met the American Diabetes Association criteria (20) for T2D (e.g., hemoglobin A1c [A1C] >6.5% and fasting glucose >126 mg/dl), with diagnosis confirmed by their primary medical clinician. We included patients with well-controlled T2D if they had low physical activity because such inactivity still placed them at risk for diabetes complications and medical events (21).

2. Low baseline physical activity. We defined low physical activity as ≤150 min/wk of moderate to vigorous physical activity (MVPA), consistent with American Diabetes Association physical activity recommendations (22). This criterion was assessed at screening via the International Physical Activity Questionnaire (23).

We excluded patients with a) cognitive impairment, assessed using a six-item screen (24), b) a medical condition likely to lead to death within 6 months, c) inability to communicate in English, d) inability to participate in MVPA (e.g., because of severe arthritis), or e) lack of telephone access.

Recruitment and Enrollment

Participants were patients with T2D seen in the medical center’s primary care clinics, identified via electronic medical record. For primary-care-clinician–approved patients, phone screening for study criteria was conducted. Patients who were eligible and interested in participation attended an initial in-person study visit, at which they provided written informed consent, completed self-report outcome measures, and received an accelerometer to wear for 7 days to measure baseline physical activity. Participants then attended a second baseline study visit, returned the accelerometer, and were assigned to a condition via allocation by minimization (25).

Allocation by minimization is a method to improve matching of participant characteristics between groups in small trials. Participants were initially randomly assigned to groups. Once a minimum of eight participants had been randomly assigned to each group, a prospectively created algorithm created by the study biostatistician (B.C.H.) selected the study condition for subsequent participants to optimize matching on age (<65 or 65+ years), sex, baseline physical activity (mean = <10 or 10+ min MVPA/d), and baseline medical comorbidity (age-adjusted Charlson Comorbidity Index (26) score of <4 or 4+); cutoffs for activity and comorbidity were generated based on median scores from the initial set of participants randomized to the groups. We selected these variables for the allocation algorithm because of their potential effects on physical activity. Study coordinators and participants learned contemporaneously about group allocation after entry of participant data into the algorithm.

After condition assignment, participants met with a study interventionist (trained psychologist), who provided a condition-specific (PP-MI or MI-enhanced condition) treatment manual (Supplemental Digital Content Tables 2 and 3, http://links.lww.com/PSYMED/A649), reviewed the program’s rationale and the first week’s material, and assigned an initial exercise/activity. All participants received a pedometer to assist with increasing physical activity. The remainder of the intervention was delivered via phone.

Interventions

Positive psychology–motivational interviewing

Each week, participants used their treatment manual to perform assigned weekly activities and completed 30- to 45-minute phone sessions with a study interventionist. The PP-MI intervention contained a PP component that focused on the completion of PP-based activities and integration of related skills into daily life, and a separate MI component that used MI principles (and goal setting) to specifically promote physical activity (Supplemental Digital Content Table 4, http://links.lww.com/PSYMED/A649).

The PP exercises were chosen from the literature (27) and the team’s prior work delivering PP interventions (15,19). Each PP session involved a specific weekly topic and exercise (e.g., recalling positive events) adapted to T2D. The first 3 weeks/sessions focused on gratitude and meaning-based activities, and the fourth week was devoted to consolidating those activities and skills and using them in daily life. The remaining sessions focused on leveraging past successes, personal strengths, and altruism, with a final session that discussed using these skills in daily life postintervention. Interventionists explained each PP exercise via a guided manual review; participants then completed exercise(s) during the week and wrote about the exercise and its effects. The following week, the interventionist reviewed the exercise and introduced a new PP exercise.

For the MI-informed portion of the intervention, interventionists used an overall “5A’s” strategy (Ask, Advise, Assess, Assist, Arrange; see the following discussion) based in behavior change theory as part of health behavior interventions in medical settings. In addition, each week, a specific MI-related topic (e.g., identifying pros and cons of increasing activity, setting SMART [Specific, Measurable, Attainable, Relevant, and Time-bound] goals) was also reviewed, and in-session activities focused on these skills. Participants set a weekly physical activity goal that was reviewed during phone sessions.

The PP-MI program was adapted to T2D in several ways. The introductory section of the treatment manual focused on living with diabetes, links between psychological factors and diabetes, and how improving physical activity could improve T2D outcomes. A new PP activity, on perseverance, was specifically developed from our prior work with T2D patients that identified the need to make persistent and often difficult changes to manage this chronic illness. Interventionists also focused on T2D-specific issues during integration weeks that focused on long-term goals and benefits with respect to well-being, energy, and glycemic control.

Phone sessions were recorded. At weekly study interventionist meetings, interventionists listened to sessions with the team’s intervention supervisors (C.M.C., R.A.M.) and received feedback on protocol adherence; these supervisors also rated randomly selected sessions for fidelity to the PP and MI intervention components using a customized 14-point team-created scale (Supplemental Digital Content Table 5, http://links.lww.com/PSYMED/A649) developed and used in our prior studies (28). The PP-focused portion of the scale contained elements related to maintaining the structure/focus of the intervention, discussion of the week’s PP-based topic, and integration of PP-related skills into daily life.

MI-Enhanced Behavioral Counseling Control Condition

An MI-enhanced behavioral counseling intervention was selected to provide a relevant, time- and attention-matched control condition. The intervention provided health education content and used MI principles (e.g., considering pros/cons and importance/confidence in change) to assist participants in understanding and making changes to important cardiometabolic health behaviors, including physical activity, diet, medication adherence, and overall diabetes self-care. It had a parallel structure to the experimental arm. Participants received an intervention manual that combined MI-specific topics with health education content (e.g., education about self-monitoring, benefits of physical activity in reducing diabetes complications) and used the 5A’s approach, as in PP-MI. Participants had weekly phone sessions with their study interventionist to learn about diabetes self-care and health behaviors, discuss their current level of engagement in these behaviors, develop methods to improve engagement, problem-solve barriers, and identify resources to improve adherence. The interventionists used MI principles throughout these sessions. The MI-enhanced condition did not contain specific PP-related content, and the longer duration of MI/health education (30 minutes), compared with the MI component of PP-MI, was used for further discussion of weekly topics (e.g., setbacks and changes in readiness), education about T2D, and barriers/facilitators of health behaviors (Supplemental Digital Content Table 6, http://links.lww.com/PSYMED/A649).

The same interventionists were used for both groups to avoid interventionist-specific effects on outcomes. As in PP-MI, MI-enhanced sessions were recorded, and study interventionists and supervisors listened to these sessions at weekly meetings to ensure that the intervention was delivered with high fidelity and without contamination across conditions; randomly selected MI-enhanced sessions were rated for fidelity as in PP-MI using an established MI fidelity scale (29), with additional elements related to using MI principles and tools (e.g., expressing empathy and developing discrepancy; Supplemental Digital Content Table 5, http://links.lww.com/PSYMED/A649). The supervisors also ensured that interventionists avoided use of PP-based content or principles in the MI-enhanced condition during their review of sessions.

For all participants, we provided specific verbal and written guidance about symptoms of hypoglycemia using handouts and protocols adapted from prior National Institutes of Health studies (30); and at calls and follow-up assessments, interventionists and study staff queried participants at risk for hypoglycemia (e.g., those prescribed sulfonylureas) about symptoms of hypoglycemia.

Outcome Assessments and Study Measures

Data were collected at baseline and throughout the 16-week study period. Baseline participant characteristics (sociodemographics, medical history, medications) were collected at the in-person baseline study visit, with information supplemented using the medical record. Baseline study outcome measures (including self-report measures, accelerometer-measured physical activity, and medical outcomes [blood pressure, body mass index, A1C]) were likewise collected at the baseline study visit and at an 8-week postintervention in-person assessment with blinded study coordinators. To reduce participant burden, a 16-week follow-up assessment was conducted by phone; physical activity at 16 weeks was assessed via accelerometers that were mailed to participants, worn for 1 week, and returned by mail. Medical outcomes were not collected at 16 weeks in this initial trial that was focused on feasibility, positive affect, and physical activity.

The primary aim of the BEHOLD-8 study was to assess PP-MI feasibility and acceptability. For feasibility, interventionists recorded whether participants successfully completed phone sessions each week (i.e., completion of PP-based activity plus completion of the phone session [with MI-based goal setting]). For acceptability, during weekly phone calls, participants separately rated the ease and helpfulness (utility) of the PP exercise and MI topic discussed during the prior week on a 0–10 Likert scale (0, very difficult, totally unhelpful; 10, very easy, very helpful), for four total scores each week.

A key secondary aim of this trial was to explore between-group differences in positive affect (main psychological target) and physical activity (main health behavior target, measured via accelerometer) improvements at 8 and 16 weeks. Positive affect, the proximal target of the intervention and our main psychological outcome given its links to health outcomes and sensitivity to change (31), was measured via the positive affect subscale of the Positive and Negative Affect Schedule (PANAS (32); internal consistency [α] in this sample = .90) regarding participants’ experience in the past week.

Physical activity, the main overall intervention target, was measured via waist-worn Actigraph GT3X+ accelerometers (Actigraph, Pensacola, FL) for 7 days at baseline, week 8, and week 16. Consistent with prior research (28), participants were required to have 8 hours of wear time for 4+ days; accelerometers were returned to participants for additional wear as needed. MVPA and steps were the main study measures of activity. We used MVPA given its links to health outcomes, including mortality. Although GT3X+ cutoffs for MVPA have varied, with lower MVPA cutoffs for older adults (e.g., 1040 counts/min) in some cases (33), we chose 1952 counts/min for MVPA given that we expected a mixed-age (midlife and older adults) cohort and that it seems to remain the most commonly used MVPA criterion in these populations (34). We also examined total steps, given increasing data that even lighter intensity activity is associated with superior medical prognosis (35).

Additional psychological outcomes included dispositional/trait optimism, measured via the Life Orientation Test—Revised (36) (α = .76), resilience (measured via the Brief Resilience Scale (37); α in this sample = .86), and depression and anxiety measured via the Hospital Anxiety and Depression Scale (38) subscales for depression and anxiety (α = .78 [depression] and α = .81 [anxiety]).

Additional functional, behavioral, and medical outcome measures included physical function (PROMIS-physical function 20-item scale (39); α = .89) and exercise self-efficacy (Self-Efficacy for Exercise scale (40); α = .90). Blood pressure, body mass index, and A1C were collected by trained research nurses using standardized protocols in our center’s Translational and Clinical Research Center; A1C was assessed via LabCorp (Middleborough, MA) or our hospital’s Diabetes Research Center, an International Federation of Clinical Chemistry and Laboratory Medicine reference laboratpry.

Statistical Analysis

For data analysis, descriptive statistics (means, standard deviations [SDs], proportions) were used to summarize baseline participant characteristics, with χ² analyses, Fisher exact tests, and independent-samples t tests used to examine between-group differences. For feasibility (primary aim), we recorded the mean number of completed sessions (of eight possible weekly sessions). For acceptability, we calculated the means and SDs of the ease/utility scores for the PP and MI components of the intervention, for a total of four separate mean scores. A priori, we set 70% completion of assigned sessions and mean ratings of 7.0/10 on ease/utility scales as benchmarks for feasibility and acceptability, based on prior work on psychological-behavioral interventions using similar scales and thresholds (15,28).

For our secondary aim examining between-group differences in study outcomes, we used an intent-to-treat model. For all study outcomes, we used mixed-effects regression models with an unstructured covariance matrix to examine between-group differences in change from baseline on each outcome at 8 and 16 weeks, controlling for the four allocation variables (age, sex, comorbidity, and baseline MVPA).

For our main secondary outcome measures assessed between groups (MVPA, steps, and positive affect), we used a two-tailed α = .05 as a threshold for statistical significance in this initial trial. For all other outcomes, to prevent the risk of type I error, we did not test for statistical significance. For all between-group outcomes, given that this study was not designed to detect significant between-group differences, we calculated ES differences by dividing the coefficient (estimated mean difference [EMD]) by the estimated SD of the residual of the mixed model at the time point of interest.

To assess whether change in positive affect measured by the PANAS-mediated change in MVPA between week 0 and week 8, we used a series of linear regression analyses to assess the total intervention effect on change in MVPA, the direct effect on change in MVPA, and the indirect effect on change in MVPA mediated through the PANAS. In addition to using this traditional approach to mediation analysis (41), bootstrapping was used to create a 95% confidence interval for these total, direct, and indirect effects. All analyses were performed via Stata 15.2 (StataCorp, College Station, TX).

For sample size calculations for feasibility and acceptability outcomes, we used prior studies of PP-based interventions in cardiac patients. In the most recent such study, 84% of all possible sessions were completed (15); using these data and 30 participants assigned to PP-MI, this study was powered at greater than 80% to detect a true proportion of ≥70% sessions completed assuming a moderate SD of 15%. For acceptability, using prior ratings for ease and utility of sessions (mean [SD] = 8.1 [2.3]) (15), this study had greater than 95% power to detect mean ratings of ≥7.0 for each of the ease and utility scales. This initial study was not designed to detect statistically significant between-group differences in study outcomes with planned N = 60.

RESULTS

Sixty eligible patients (PP-MI: n = 30; MI alone: n = 30) were enrolled and allocated to a condition (CONSORT diagram, Figure 1). Baseline sociodemographic, medical, and psychological characteristics are provided in Table 1. The mean (SD) age of participants was 64.4 (10.1) years, 31 (52%) were women, and 45 (75%) were non-Hispanic White. Self-report follow-up data were obtained from 58 (97%) of participants at one or both time points (n = 58 at 8 weeks, n = 56 at 16 weeks), and adequate accelerometer data were obtained in 56 (93%) of participants. Serious adverse events (medical hospitalizations) did not differ between groups (n = 1 [PP-MI], n = 0 [control]); there were no hypoglycemia events requiring intervention in either group.

FIGURE 1.

Study flow diagram. Completion of self-report assessments with blinded study staff was distinct from completion of Week 8 session with study interventionist. MVPA = moderate to vigorous physical activity; PP = positive psychology; MI = motivational interviewing.

TABLE 1.

Baseline Participant Characteristics

Characteristic	Overall	PP-MI	MI Alone	Test Statistic	p
Sociodemographic characteristics
Age, M (SD), y	64.4 (10.1)	65.3 (10.6)	63.5 (9.8)	t = −0.68	.50
Female sex	31 (51.7)	16 (53.3)	15 (50.0)	χ2 = 0.07	.80
Non-Hispanic White	45 (75.0)	24 (80.0)	21 (70.0)	χ2 = 0.80	.37
Medical characteristics
Neuropathy	13 (21.7)	5 (16.7)	8 (26.7)	χ2 = 0.88	.35
Nephropathy	16 (26.7)	10 (33.3)	6 (20.0)	χ2 = 1.36	.24
Hyperlipidemia	58 (96.7)	28 (93.3)	30 (100)	a	.49
Hypertension	54 (90.0)	28 (93.3)	26 (86.7)	a	.67
Coronary artery disease	11 (18.3)	7 (23.3)	4 (13.3)	a	.51
Charlson Comorbidity Index (age-adjusted), M (SD)	4.1 (1.9)	4.1 (1.8)	4.1 (1.9)	t = 0.07	.95
Medications at enrollment
Metformin	46 (76.7)	22 (73.3)	24 (80.0)	χ2 = 0.37	.54
Insulin	9 (15.0)	4 (13.3)	5 (16.7)	a	1.0
Sulfonylureas/meglitinides	20 (33.3)	6 (20.0)	14 (46.7)	χ2 = 4.80	.028
Antidepressant	15 (25.0)	7 (23.3)	8 (26.7)	χ2 = 0.09	.77
Anxiolytic	7 (11.7)	4 (13.3)	3 (10.0)	a	1.0

PP = positive psychology; MI = motivational interviewing; M (SD) = mean (standard deviation).

Data are presented as n (%) unless noted.

^aFisher exact test used; no test statistic.

Feasibility and Acceptability

PP-MI participants completed a mean (SD) of 7.4/8 (1.8) sessions (92% of all possible sessions). In addition, 98% of MI-enhanced behavioral counseling intervention sessions were completed. For PP-MI acceptability, participants’ mean (SD) ratings (0–10 scale) of PP-MI activity ease and utility were 8.6 (1.8) and 8.8 (1.5), respectively, for the PP component, and 8.5 (1.9) and 8.6 (2.0) for MI; these differences were not statistically significant.

Psychological and Functional Outcomes

Regarding between-group differences in these study outcomes (Table 2), PP-MI was associated with approximately medium magnitude ES improvements in change from baseline PANAS (positive affect) score at both 8 and 16 weeks (8 weeks: EMD = 3.07 [SE = 1.41], p = .029, ES = 0.44; 16 weeks: EMD = 2.92 [SE = 1.73], p = .092, ES = 0.42) compared with the MI-enhanced control condition. The intervention was associated with small to medium ES improvementsinresilience(Brief Resilience Scale;ES= 0.09–.41), and it had mixed effects on trait optimism, depression, and anxiety.

TABLE 2.

Between-Group Differences in Change From Baseline on Study Outcome Measures

	8 wk					16 wk
Measure	EMD	SE	z	p	ES	EMD	SE	z	p	ES
Positive affect
Positive affect (PANAS) Physical activity	3.07	1.41	2.19	.029*	0.44	2.92	1.73	1.69	.092†	0.42
MVPA, min/d	13.05	5.00	2.61	.009*	1.24	7.96	4.53	1.75	.079†	0.75
Steps per day	1554	649	2.40	.017*	1.02	808	648	1.25	.21	0.53

	8 wk				16 wk
Measurea	EMD	SE	z	ES	EMD	SE	z	ES
Additional psychological measures
Optimism (LOT-R)	0.18	0.76	0.23	0.04	−0.54	0.84	−0.64	−0.12
Resilience (BRS)	0.19	0.65	0.30	0.09	0.85	0.73	1.16	0.41
Depression (HADS-D)	0.45	0.67	0.67	0.13	−0.79	0.71	−1.11	−0.22
Anxiety (HADS-A) Additional functional/behavioral measures	−0.07	0.64	−0.10	−0.02	0.32	0.78	0.41	0.08
Exercise self-efficacy (SEE)	8.81	5.71	1.54	0.43	14.64	5.26	2.78	0.72
Physical function (PF-20)	−1.72	1.16	−1.48	−0.28	0.92	1.36	0.68	0.15
Medical outcomes (8 wk only)
Hemoglobin A1c, %	−0.14	0.27	−0.50	−0.09	—	—	—	—
Systolic BP, mm Hg	−2.27	3.93	−0.58	−0.14	—	—	—	—
Diastolic BP, mm Hg	−2.77	2.75	−1.01	−0.26	—	—	—	—
Body mass index, kg/m2	0.27	0.25	1.09	0.05	—	—	—	—

EMD = Estimated mean difference; ES = effect size; PANAS=Positive Affect Negative Affect Schedule; MVPA = moderate to vigorous physical activity; LOT-R = Life Orientation Test, Revised; BRS = Brief Resilience Scale; HADS=Hospital Anxiety and Depression Scale (HADS-A = Anxiety Subscale, HADS-D = Depression); SEE = Self Efficacy for Exercise scale; PF-20 = PROMIS Physical Function 20-item measure; BP = blood pressure.

^*p < .05.

^†p < .10.

^aTests of statistical significance were only performed for the main secondary outcomes of MVPA, steps, and positive affect given the sample size and focus on feasibility in this trial.

Regarding physical activity, compared with the MI-enhanced control condition, the PP-MI intervention was associated with substantially greater (medium to large ES difference) improvements in MVPA, reaching statistical significance at 8 weeks (8 weeks: EMD = 13.05 min/d [SE = 5.00], p = .009, ES = 1.24; 16 weeks: EMD = 7.96 [SE = 4.53], p = .079, ES = 0.75). Likewise, PP-MI participants took a significantly greater number of steps per day at 8 weeks, with some reduction of between-group differences at 16 weeks (8 weeks: EMD = 1554 steps/d [SE = 649], p = .017, ES = 1.02; 16 weeks: EMD = 808 steps/d [SE = 648], p = .21, ES = 0.53). See Supplemental Digital Content Table 7 (http://links.lww.com/PSYMED/A649) for mean values by group at all time points for positive affect and physical activity outcomes.

The PP-MI intervention was also associated with approximately medium ES greater improvements in exercise self-efficacy as measured by the Self Efficacy for Exercise scale (ES = 0.43 at 8 weeks and ES = 0.72 at 16 weeks). Between-group effects on other psychological, functional, behavioral, and medical outcomes (Table 2), including blood pressure, body mass index, and A1C, were mixed, with PP-MI generally associated with slightly greater improvements.

On our analysis examining mediation of MVPA change between weeks 0 and 8 by change in the PANAS, we found that the coefficient of the total effect on MVPA at 8 weeks was 13.46 minutes (95% confidence interval = 3.59 to 24.18), the coefficient of the direct effect of the intervention on MVPA was 11.13 (3.00 to 20.16), and the coefficient of the indirect effect of the intervention on MVPA change mediated through the PANAS/positive affect was 2.33 (−0.89 to 7.34), suggesting that changes in positive affect appeared to account for approximately 17% of the change in MVPA.

DISCUSSION

In this initial trial of an 8-week phone-delivered, combined PP-MI intervention to promote well-being and physical activity among inactive patients with T2D, we found that PP-MI was feasible and well-accepted. PP-MI participants completed more than 90% of all possible sessions and provided mean scores of greater than 8/10 on ratings of intervention ease and utility for both intervention components, well above our a priori thresholds for feasibility/acceptability. These findings are consistent with—and even more robust than—our prior findings on such metrics for PP-based interventions in clinical settings (42), and they suggest that this program may be a viable option for this patient population, for whom low physical activity is a risk factor for complications, cardiovascular disease, and mortality. MI-enhanced sessions were also completed at high rates, suggesting strong engagement with this control condition.

In addition, the PP-MI intervention was associated with approximately medium-sized effects on improvement in positive affect, the proximal target of the PP intervention component, compared with the intensive control condition. Such findings are consistent with prior work on PP-based clinical interventions (43). Modifying positive affect in T2D patients may have important implications, as higher positive affect has been associated with lower risk of cardiac events and overall mortality in healthy persons (13) and reduced mortality specifically in T2D (31).

PP-MI also was associated with greater physical activity as measured by accelerometer, with PP-MI participants completing 8 to 13 more minutes of MVPA per day and taking 800 to 1550 more steps per day than those in the MI-enhanced behavioral counseling condition. These findings are consistent with prior work illustrating the links between positive psychological well-being and greater physical activity in healthy individuals, medically ill persons, and patients with T2D (12,13). Such findings are also consistent with our initial randomized trial of PP-MI in patients after an acute coronary syndrome, which had highly similar findings regarding effects on positive affect and physical activity (15). These findings add to the literature by extending this work to a chronic condition experienced by more than 27 million Americans and by comparing PP-MI to a time-matched, MI-enhanced, diabetes-specific intervention. It is critical to note that this study was an initial, feasibility-focused trial with a relatively small sample, and therefore, larger studies focused on efficacy must be conducted.

The observed magnitude of change in physical activity was also similar to other behavioral interventions for individuals with T2D. However, many of these prior interventions used much more intensive, often in-person, interventions and had less rigorous control conditions. For example, Plotnikoff and colleagues (44) compared a 10-week in-person physical activity intervention, followed by 10 additional weeks of smartphone-based treatment, to a waitlist control. They found an EMD of 1330 steps (d = 0.67) at 10 weeks, which decreased to 728 steps (d = 0.56) at 20 weeks. A broader meta-analysis of a wide range of physical activity interventions in T2D likewise found an average ES of 0.70 on objectively measured physical activity for interventions shorter than 6 months (11).

These changes in physical activity, if confirmed in a larger trial, are likely to have clinical significance. There seems to be a linear dose-response curve between leisure-time physical activity and lower mortality, even at lower levels of activity (45), and MVPA improvements on the order of 10 minutes per week, as seen in this project, are associated with mortality reductions (46). In this trial, such improvements would increase participants (who had a mean of roughly 75 minutes MVPA/wk at baseline) nearly to the recommended 150-min/wk MVPA threshold. Larger, well-powered studies must be conducted to confirm these findings.

The intervention’s effects on positive affect and physical activity in this feasibility trial did somewhat wane at 16 weeks. This suggests a potential benefit from booster intervention sessions beyond the initial 8-week period. In a prior factorial design trial examining PP intervention components in cardiac patients, we found that adding booster sessions to an initial 8-week program was associated with significantly greater effects on MVPA (28). Such additional postintervention content could be delivered via phone sessions or by text messages, which have been linked to improvements in weight loss among persons with obesity when combined with phone contact (47).

As noted, this was an initial controlled pilot trial that was designed to assess feasibility and acceptability, and larger and longer studies are needed to better understand the nature of the intervention’s effects and whether such effects might be sustained long-term, as it is maintenance of physical activity that is associated with superior health outcomes (48). If PP-MI improves positive affect and physical activity in future trials, these findings could have implications for clinical practice. PP-based interventions are simple, typically require minimal provider training, and can be delivered remotely, and MI training is available widely, although it does require systematic initial training and a persistent ongoing focus on fidelity for effective delivery. Such a program could be a broadly applicable, low-cost, and relatively low-burden intervention for inactive T2D patients who are at risk for adverse medical outcomes.

This study had several strengths, including ongoing fidelity assessments, use of a relevant, active control condition, plus pedometer provision, and objective assessments of physical activity. The study also had several limitations. It was performed in a single urban academic medical center, and the intervention was delivered by trained psychologists, potentially limiting clinical implementation in front-line settings, although in prior work, our PP and PP-MI interventions have been delivered by social workers and bachelor’s-level clinicians with high fidelity and to good effect (15,16). The control condition, although MI based, attention matched, and delivered systematically, was not as intensive as some MI programs (and did not focus solely on physical activity), and future studies could use even more intensive and matched MI programs to assess the differential effect of the PP-MI program. Finally, this initial trial also had a relatively small sample and relatively short (16 week) follow-up.

In summary, a phone-based PP-MI program to promote well-being and physical activity among inactive patients with T2D was feasible and well accepted, and it was associated with beneficial effects on positive affect and physical activity compared with an attention-matched, MI-enhanced control condition. Additional studies are required to more definitively assess impact on activity, glycemic control, and prevention of diabetes complications.

Glossary

BEHOLD-8

Boosting Emotional well-being and Happiness in Outpatients Living with Diabetes 8-week trial

EMD

estimated mean difference

ES

effect size

MI

motivational interviewing

MVPA

moderate to vigorous physical activity

PANAS

Positive and Negative Affect Schedule

PP

positive psychology

SD

standard deviation

T2D

type 2 diabetes