This study demonstrates that a literacy and numeracy-focused diabetes intervention may contribute to improving glycemic control and diabetes self-management self-efficacy. However, the impact of the literacy- and numeracy-focused program on glycemic control was modest compared with that of an already strong enhanced diabetes care program control group. In addition, although patients continued to have improved glycemic control compared with baseline values, the intervention was not able to show sustained benefits above the control setting 3 months after completion of the program.
Training diabetes providers in improved health communication skills may help to improve patient understanding of health information and self-management behavior. The DLNET used in this study provides a useful comprehensive customizable resource to facilitate diabetes education and management. Patients often desire diabetes materials developed for low literacy skills (22
). The DLNET uses text at the sixth-grade literacy level, as opposed to much of the existing health information including materials specific to diabetes, which are often at a higher reading level (23
), and also incorporates many other principles of clear communication (24
). The DLNET can be used as a core element for both initial and on-going diabetic patient education programs aimed to counsel patients of all skill levels.
Although we found that intervention group participants had an improvement in their glycemic control during the period of intervention delivery, this differential improvement was not sustained after the program concluded. One explanation may be the level of patient interaction with the health care system during the enhanced diabetes care program and the subsequent observation period. Although the total number of visits did not differ between intervention and control groups during the entire 6 months, patients in both groups did see a health provider more often during the 3 months of the intervention compared with the observation period after the intervention period. This result suggests that successful reduction in A1C may require a persistent level of intervention over time and also may suggest that our program performs better as a disease management program than as a self-care training program.
Other explanations for why there was no difference seen between intervention and control groups at the 6-month interval, as well as the modest difference at the 3-month interval, are differential loss to follow-up and the highly active control arms in this study. Patients in the control group were less likely to complete the study, and those who did not complete it may have had worse glycemic control. In addition, patients in the control arms participated in an enhanced diabetes care program that provided additional diabetes management above what is usually provided by diabetes physicians. This included multiple visits with other providers experienced in addressing physiological and social factors associated with glycemic control. In addition, the effectiveness of the intervention differed between the two study sites. Study participants in the control arm at UNC had much less improvement in A1C than that for all other study groups. This difference may be explained, in part, by different measured and unmeasured patient characteristics or by differing provider management practices at each study site.
Patient self-efficacy of diabetes self-management and satisfaction improved for all groups. Because nearly all patients reported an improvement, we were unable to demonstrate a significant difference between the intervention and control groups in this study. Participation in the trial itself may have contributed to the improvement in both self-efficacy and satisfaction for control group patients.
There are several limitations to this study. First, this study was performed and initially powered as two separate, yet coordinated, randomized trials; however, because of the similar hypotheses and design, the decision to analyze combined results of the two trials was made before the completion of data collection at either site. Second, at one of the two sites (VUMC), there were significant differences between intervention and control groups in several patient characteristics. This unequal randomization could result in residual confounding. To address this possibility we performed analyses adjusting for potential confounding variables, and the findings were consistent with the unadjusted results. Third, there were patients (n = 30; 15%) who did not complete evaluation of the primary outcome at one of the two designated time intervals. Although this limits cross-sectional evaluations at those times, we used ordinary least squares regression models with multiple imputations to use all data points for participants in the study and minimize the potential bias of missing information. Fourth, many patients declined participation. This may limit the generalizability of our findings, as they may not fully represent all patients with diabetes. Finally, this trial was not adequately powered to evaluate differences in the effect of the intervention by patient literacy or numeracy status.
Among patients with diabetes, literacy and numeracy are important characteristics that have been associated with glycemic control and may play a significant role in the optimization of diabetes care. Use of materials designed to facilitate diabetes education and empower patients to effectively self-manage their condition within an environment by applying clear communication principles is a fundamental component of comprehensive diabetes care. Strategies to enhance effective communication between patients and providers transferring health literacy and numeracy-sensitive information need to be further studied to identify ways to improve care for patients with diabetes.