This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work, first published in JMIR Diabetes, is properly cited. The complete bibliographic information, a link to the original publication on http://diabetes.jmir.org/, as well as this copyright and license information must be included.
High levels of psychosocial distress are correlated with worse glycemic control as measured by glycosylated hemoglobin levels (HbA1c). Some interventions specifically targeting diabetes distress have been shown to lead to lower HbA1c values, but the underlying mechanisms mediating this improvement are unknown. In addition, while type 2 diabetes mellitus (T2D) disproportionately affects low-income racial and ethnic minority populations, it is unclear whether interventions targeting distress are differentially effective depending on participants’ baseline characteristics.
Our objective was to evaluate the mediators and moderators that would inform interventions for improvements in both glycemic control and diabetes distress.
Our target population included 290 Veterans Affairs patients with T2D enrolled in a comparative effectiveness trial of peer support alone versus technology-enhanced peer support with primary and secondary outcomes including HbA1c and diabetes distress at 6 months. Participants in both arms had significant improvements in both HbA1c and diabetes distress at 6 months, so the arms were pooled for all analyses. Goal setting, perceived competence, intrinsic motivation, and decisional conflict were evaluated as possible mediators of improvements in both diabetes distress and HbA1c. Baseline patient characteristics evaluated as potential moderators included age, race, highest level of education attained, employment status, income, health literacy, duration of diabetes, insulin use, baseline HbA1c, diabetes-specific social support, and depression.
Among the primarily African American male veterans with T2D, the median age was 63 (SD 10.2) years with a baseline mean HbA1c of 9.1% (SD 1.7%). Improvements in diabetes distress were correlated with improvements in HbA1c in both bivariate and multivariable models adjusted for age, race, health literacy, duration of diabetes, and baseline HbA1c. Improved goal setting and perceived competence were found to mediate both the improvements in diabetes distress and in HbA1c, together accounting for 20% of the effect of diabetes distress on change in HbA1c. Race and insulin use were found to be significant moderators of improvements in diabetes distress and improved HbA1c.
Prior studies have demonstrated that some but not all interventions that improve diabetes distress can lead to improved glycemic control. This study found that both improved goal setting and perceived competence over the course of the peer support intervention mediated both improved diabetes distress and improved HbA1c. This suggests that future interventions targeting diabetes distress should also incorporate elements to increase goal setting and perceived competence. The intervention effect of improvements in diabetes distress on glycemic control in peer support may be more pronounced among White and insulin-dependent veterans. Additional research is needed to understand how to better target diabetes distress and glycemic control in other vulnerable populations.
Diabetes distress, or the negative emotional and behavioral responses that can occur as a result of having a demanding chronic illness like diabetes, is an increasingly recognized psychosocial factor influencing diabetes self-management [
While the link between high levels of diabetes distress and higher HbA1c has been well established [
Equally important is understanding the characteristics of participants who benefit the most from these interventions. Prior studies have found that patients who are younger, female, have longer duration of diabetes, and are of ethnic minority status, particularly African Americans, have higher diabetes distress levels [
Peer support interventions, in which an individual with prior experience or knowledge who has been successful in their own self-management behaviors serves as a supportive mentor for a target population of patients with similar ethnic or socioeconomic background, are emerging as an important tool for patients with diabetes mellitus, particularly for vulnerable patient populations [
In this trial, participants were randomized to peer coaches without any additional eHealth tools or to peer coaches using an individually tailored, web-based educational tool (iDecide) over the course of 6 months. This tool had interactive features to allow participants to understand their personal diabetes risk profile as well as explore options for medications based on cost, effectiveness, and side effects [
A mediator analysis is one method to explore the psychosocial mechanisms that link diabetes distress and glycemic control. In such an analysis, a conceptual model is created that hypothesizes potential targets, or mediators, along the mechanistic pathway that an intervention must include in order to be successful in achieving the desired outcome. In the previously mentioned RCT by Heisler et al [
Conceptual model for hypothesized mediators and moderators of improved glycemic control in a peer coaching intervention.
A moderator analysis can be used to evaluate the characteristics of participants who benefited the most from the peer support intervention of reducing diabetes distress to improve glycemic outcomes. These characteristics are called moderators as they help inform differential effects in the relationship between an independent and dependent variable and hence identify potential modifiers and/or target population for the intervention. In our conceptual model shown in
In an intervention that improves both diabetes distress and glycemic control, are improvements in diabetes distress correlated with improvements in HbA1c (main effect)?
Do goal setting, perceived competence, intrinsic motivation, and decisional conflict work individually or in combination to mediate the relationship between diabetes distress and glycemic control (mediating effect)?
Does age, race, education, employment, health literacy, duration of diabetes, HbA1c, insulin use, diabetes-specific social support, or depression moderate the relationship between diabetes distress and glycemic control (moderating effect)?
The target population for this study included veterans with T2D and high baseline HbA1c values enrolled in a comparative effectiveness RCT of peer support versus technology-enhanced peer support. The description of recruitment, intervention, outcomes, and results of this RCT have been described previously [
Diabetes distress: Measured, analyzed, and reported using the 2-item validated Diabetes Distress Scale–2, which assesses feelings that living with diabetes is overwhelming and/or that the participant is failing in their diabetes management [
Goal setting: Measured, analyzed, and reported using the 3-item goal setting subscale of the Patient Assessment of Chronic Illness Care, which assesses whether participants were aided in setting goals for self-management and, if so, whether an action plan was developed [
Perceived competence: Measured, analyzed, and reported using the 4-item validated Perceived Competence scale, which assesses the extent to which a participant feels confident and capable of meeting the challenges of diabetes self-management [
Intrinsic motivation: Measured, analyzed, and reported using the intrinsic motivation subscale of the Treatment Self-Regulation Questionnaire, which assesses the extent to which participants feel self-motivated to improve their health behaviors [
Decisional conflict: Measured, analyzed, and reported using the 1-item validated Decisional Conflict Scale, which assess the extent to which a participant is satisfied with their medication options for diabetes [
In the RCT, both arms demonstrated improved diabetes distress and HbA1c values at 6 months. Therefore, in this study, participants in both arms were combined to investigate goal setting, perceived competence, intrinsic motivation, and decisional conflict as potential mediators, as shown in
Descriptive statistics were used to evaluate frequencies and means of baseline participant characteristics, and paired
We next assessed the role of goal setting, perceived competence, intrinsic motivation, and decisional conflict as mediators between the change in diabetes distress and the change in HbA1c at 6 months. Multivariable linear regression models were used with the covariate adjustments of age, race, health literacy, duration of diabetes, and baseline HbA1c. This is conceptualized by the mediation model in
Relationship a: between diabetes distress (independent variable) and all potential mediators (dependent variables)
Relationship b: between all potential mediators (independent variable) and HbA1c
The potential mediators that were found to be significantly associated with the change in diabetes distress and HbA1c at 6 months were selected for formal mediation testing by using seemingly unrelated linear regression techniques [
Finally, sociodemographic factors (age, race, highest attained education, income, employment) and baseline clinical and psychosocial attributes (health literacy, HbA1c, duration of diabetes, insulin use, diabetes-specific social support, depressive symptoms) were assessed as potential moderators of the relationship between change in diabetes distress and change in HbA1c at 6 months. Multivariable linear regressions include an interaction term between the change in diabetes distress at 6 months and each of the potential moderators as well as those variables themselves. The change in HbA1c at 6 months was the independent variable in these models and covariates included age, race, health literacy, duration of diabetes, and baseline HbA1c except where the variable was tested as a moderator. This moderator model is conceptualized in
A total of 290 veterans with T2D were enrolled in the two intervention arms of the RCT. Baseline characteristics of the full cohort are shown in
Baseline characteristics of all participants (n=290).
Characteristic | Value | |
Age in years, mean (SD) | 63 (10.2) | |
|
||
Female | 7 (2) | |
Male | 283 (98) | |
|
||
Black | 181 (62) | |
White | 106 (37) | |
Other | 2 (0.7) | |
|
||
Employed | 74 (26) | |
Not employed | 49 (17) | |
Retired | 141 (49) | |
Disabled | 23 (8) | |
|
||
Less than high school | 12 (4) | |
High school graduate | 78 (27) | |
Some tech or vocational | 23 (8) | |
Some college or more | 177 (61) | |
|
||
1-15,000 | 61 (21) | |
16,000-30,000 | 81 (28) | |
31,000-55,000 | 59 (20) | |
56,000 and above | 46 (16) | |
Prefer not to discuss | 42 (15) | |
Baseline HBA1ca, mean (SD) | 9.1 (1.7) | |
Number of years with diabetes, mean (SD) | 15.2 (10.0) | |
Insulin use, n (%) | 171 (60) | |
Number of oral antihyperglycemic meds, mean (SD) | 1.1 (0.8) | |
Health literacy, mean (SD) | 7.0 (1.9) | |
Diabetes-specific social supportb, mean (SD) | 54.4 (14.3) | |
Depressionc, mean (SD) | 76.9 (27.0) |
aHBA1c: hemoglobin A1c.
bBased on the Diabetes-Specific Social Support Needs assessment [
cBased on the Patient Health Questionnaire–2 scaled score ranging from 0 to 100, with more positive outcomes reflected by higher numbers.
A significant association between the improvement in diabetes distress and decreased HbA1c was found in the unadjusted model (β-coefficient –0.017; 95% CI –0.028 to –0.006;
Improvement in goal setting at 6 months was associated with improvements in diabetes distress (β coefficient 0.225,
Adjusted estimates of the effect of diabetes distress on all potential mediators (relationship a) and the effect of all mediators on hemoglobin A1c (relationship b).a
Potential mediator (outcome in relationship a; predictor in relationship b) | Main predictor: diabetes distressb (relationship a) | Main outcome: hemoglobin A1cc (relationship b) | ||||
β coefficient | 95% CI | β coefficient | 95% CI | |||
Goal setting | .225 | .036 to .414 | .02 | –.009 | –.015 to .002 | .004 |
Perceived competence | .183 | .065 to.300 | .002 | –.011 | –.021 to –.001 | .03 |
Intrinsic motivation | .007 | –.127 to.141 | .91 | –.008 | –.017 to .001 | .07 |
Decisional conflict | .101 | –.053 to.255 | .20 | –.007 | –.015 to .0003 | .06 |
aDiabetes distress, hemoglobin A1c, and all potential mediators assessed as the mean change from baseline to 6 months.
bModels included diabetes distress as the independent variable and potential mediators as dependent variables; covariates include age, race, health literacy, duration of diabetes, and baseline A1c variables.
cModels included potential mediators as the independent variable and hemoglobin A1c as the dependent variable; covariates include age, race, health literacy, duration of diabetes, and baseline A1c variables.
Mediating effects of goal setting and perceived competence in the relationship between diabetes distress and hemoglobin A1c (mediator analysis).
Potential mediatora | Indirect effectb (95% CI) | Share of total effect (%) |
Goal setting | –0.002 (–0.0052 to –0.0001) | 13.3 |
Perceived competence | –0.001 (–0.0045 to –0.0002) | 6.7 |
Combination of goal setting and perceive competence | –0.003 (–0.0072 to –0.0005) | 20 |
aGoal setting and perceived competence assessed as the mean change from baseline to 6 months.
bCovariates include age, race, health literacy, duration of diabetes, and baseline hemoglobin A1c.
As shown in
Adjusted estimates on the effect of improved diabetes distress on improved glycemic control, by groups with different baseline characteristics (moderator analysis).
Potential moderator | N | Baseline mean diabetes distress (Predictor) | Baseline mean HBA1ca (Outcome) | Adjusted estimates | ||||
β coefficient for change at 6 months (within subgroup)b | Difference in β coefficients (between subgroups) | |||||||
|
||||||||
<65 | 154 | 71.7 | 9.3 | –0.019 | .002 | 0.007 | .24 | |
>65 | 136 | 74.9 | 8.8 | –0.012 | .11 | |||
|
||||||||
Black | 181 | 74.0 | 9.1 | –0.006 | .28 | 0.029 | .002 | |
White | 106 | 72.2 | 9.0 | –0.035 | <.001 | |||
|
||||||||
<HSc | 12 | 77.8 | 8.8 | 0.024 | .52 | 0.040 | .63 | |
>HS | 278 | 73.0 | 9.1 | –0.016 | .001 | |||
|
||||||||
Noned | 213 | 74.6 | 9.1 | –0.011 | .19 | 0.008 | .58 | |
Employed | 74 | 69.6 | 8.9 | –0.018 | .002 | |||
|
||||||||
<30,000 | 142 | 73.1 | 9.1 | –0.012 | .07 | 0.011 | .13 | |
>30,000 | 105 | 73.8 | 9.0 | –0.023 | .003 | |||
|
||||||||
Low | 152 | 70.4 | 9.1 | –0.026 | <.001 | 0.018 | .07 | |
High | 138 | 76.3 | 9.1 | –0.008 | .20 | |||
|
||||||||
Low | 132 | 81.9 | 8.8 | –0.013 | .10 | 0.003 | .64 | |
High | 158 | 66.0 | 9.3 | –0.015 | .01 | |||
|
||||||||
Low | 111 | 76.9 | 9.2 | –0.012 | .15 | –0.004 | .59 | |
High | 130 | 72.2 | 9.0 | –0.016 | .007 | |||
|
||||||||
<10 | 111 | 71.4 | 9.3 | –0.026 | .006 | 0.016 | .05 | |
>10 | 179 | 74.3 | 8.9 | –0.008 | .07 | |||
|
||||||||
<8.5 | 109 | 78.1 | 7.7 | –0.021 | .004 | 0.011 | .50 | |
>8.5 | 134 | 70.8 | 10.2 | –0.010 | .14 | |||
|
||||||||
No | 119 | 73.7 | 8.8 | –0.006 | .40 | 0.024 | .02 | |
Yes | 171 | 72.9 | 9.3 | –0.029 | .001 |
aHBA1c: hemoglobin A1c.
bAdjusted for age, race, health literacy, duration of diabetes and baseline hemoglobin A1c except where these variables were tested as moderators.
cHS: high school.
dIncludes not employed, retired and disabled.
eBased on scaled PHQ-2 scores (above and below scaled median value).
fBased on scaled DSS scores (above and below scaled median value).
We found that in a cohort of primarily African American veterans with T2D, improvements in diabetes distress are associated with improvements in glycemic control as measured by HbA1c. Additionally, goal setting and perceived competence are modest mediators of this effect with goal setting and perceived competence accounting for 13% and 7% of the total effect, respectively. Combined, goal setting and perceived competence account for one-fifth of the total shared effect between diabetes distress and glycemic control, suggesting that goal setting and perceived competence are important targets in the mechanistic pathway. Finally, we found that participants with certain sociodemographic and diabetes-specific characteristics are more responsive to improvements in diabetes distress with the peer support approach tested in this RCT. In particular, Caucasian veterans and veterans who require insulin are more likely to demonstrate improved glycemic control with improved diabetes distress. This is an important finding to guide the development of future interventions. Knowing which populations respond to various types of interventions is the first step in personalized care for diabetes self-management to improve both glycemic and psychosocial outcomes.
In this study, we evaluated the results of a peer support RCT for veterans with T2D that demonstrated improvements in both diabetes distress and HbA1c at 6 months to assess for potential underlying mechanisms and baseline participant characteristics that predict both psychosocial and glycemic responsiveness to the intervention. In concert with findings from findings from other studies, we found that diabetes distress is associated with HbA1c [
Importantly, we also found that perceived competence is a mediator in the pathway between diabetes distress and glycemic control. Although self-efficacy is traditionally associated with the social cognitive theory and perceived competence is an important theme in the self-determination theory, the concepts of self-efficacy and perceived competence are related and often used interchangeably [
Our study also had several important novel findings. The first is the importance of goal setting not only as a negative correlate of diabetes distress and glycemic control but also as a mediator in the pathway between diabetes distress and glycemic control. This finding highlights diabetes-specific goal setting as an important target of any intervention to improve both psychosocial and glycemic outcomes. Moreover, we found that certain baseline characteristics predict a more robust improvement of the HbA1c due to the reduced levels of diabetes distress. Race was found to a moderator, suggesting that Caucasian veterans responded more to the peer support intervention than African American patients. Prior studies suggest that peer supporters who are culturally appropriate (including concordant age, race, and gender) may be more effective peer supporters for African Americans with diabetes [
This study has several strengths. The first is that, to our knowledge, this is the first study looking at mediators and moderators between glycemic control and diabetes distress in an intervention that improves both. We incorporated robust statistical methods to assess the mediation pathway, finding that goal setting and perceived competence are important for future interventions targeting both glycemic and psychosocial outcomes for T2D. This is also one of the first studies to more specifically examine a broad array of socioeconomic and diabetes-specific characteristics that might moderate the relationship between diabetes distress and glycemic control. This is important because this can facilitate screening and targeted interventions using information readily captured by electronic medical records.
We also recognize that our study has several important limitations. First, this study was conducted in primarily African American male veterans with T2D, which limits the generalizability of our findings. It is therefore possible that, in other populations, goal setting and perceived competence have less significance in the mechanistic pathway between elevated levels of diabetes distress and worse glycemic control. Additionally, our use of brief validated scales to measure multiple complicated psychological constructs is a potential limitation, as these short-form scales did not permit in-depth investigation into different facets of these constructs. For example, we used the Diabetes Distress Scale 2 to measure diabetes distress, rather than the full 17-item Diabetes Distress Scale. Although the 2-item Diabetes Distress Scale has been found to correlate well with the larger Diabetes Distress Scale questionnaire, it does not provide subtypes of distress as it only measures emotional distress and this may have impacted our moderator analyses [
In conclusion, we found that in a peer support intervention for T2D in primarily African American male veterans both goal setting and perceived competence are important mediators in the mechanistic pathway between diabetes distress and glycemic control. Additionally, we found that this peer support intervention that improved diabetes distress was most effective in reducing HbA1c levels in White and insulin-requiring veterans with T2D. These findings are important for informing future interventions that target both psychosocial and glycemic outcomes and efforts to tailor interventions to best meet the needs of patients with different characteristics.
Diabetes distress, goal setting, perceived competence, intrinsic motivation, and decisional conflict scales.
Summary of the change in diabetes distress, change in HbA1c, and hypothesized mediators between baseline and 6 months.
hemoglobin A1c
randomized controlled trial
type 2 diabetes
Veterans Affairs
This research was supported by grants from the Veterans Affairs Health Services Research and Development Service (12-412) and the National Institute of Diabetes and Digestive and Kidney Diseases (P30DK092926 MCDTR).
KMS, HC, GP, and MH designed the study. HC and MH collected the data. KMS, HC, and CR analyzed the data. KMS wrote the first draft of the manuscript. KMS, HC, CR, GP, and MH edited the manuscript.
None declared.