Differences in the Management of Type 1 Diabetes Among Adults Under Excellent Control Compared With Those Under Poor Control in the T1D Exchange Clinic Registry

The T1D Exchange Clinic Network includes 67 U.S. pediatric and adult endocrinology practices. A registry of individuals with type 1 diabetes commenced enrollment in September 2010 (3). Each clinic received approval from an institutional review board, and informed consent was obtained from adult participants and parents or guardians of minors; assent from minors was obtained as required. Data were collected for the registry’s central database from participant medical records and by having the participant or parent complete a comprehensive questionnaire, as previously described (3).

To have a substantial separation between groups with regard to HbA_1c values, excellent glycemic control was arbitrarily defined as an average HbA_1c <6.5% in the past 12 months and fair/poor control as an average HbA_1c ≥8.5% in the past 12 months. The present report includes data on participants enrolled through 1 August 2012 who were ≥26 years of age, had type 1 diabetes for ≥2 years, and had an average HbA_1c level in the 12 months before enrollment of either <6.5 or ≥8.5%. The lower limit of 26 years was used because the registry data indicate that participants 18–25 years of age more closely resembled 13–17 year olds than older adults. Participants for whom data were not available to characterize as either a pump or injection user were excluded. In addition, users of real-time CGM were excluded because key aspects of diabetes management might differ between CGM users and nonusers, and the percentage of CGM users was small. Of the 5,475 T1D Exchange clinic registry participants meeting the non-HbA_1c inclusion criteria, 11% (n = 627) were classified as having excellent control (HbA_1c <6.5%), and 23% (n = 1,267) were classified as having fair/poor control (HbA_1c ≥8.5%); the other 65% (n = 3,581) with HbA_1c between 6.5 and 8.4% were not included in the analyses.

Data used in the analyses were obtained from a questionnaire completed by the participant, the elements of which included questions about diabetes management, lifestyle (marital and employment status, exercise), family history, and socioeconomic factors. BMI was determined from height and weight measurements at the most recent office visit. HbA_1c levels, mainly measured with point-of-care devices (60% DCA 2000 [Bayer] and DCA Vantage [Siemens], 6% other point-of-care devices, 38% laboratory, 2% unknown), were obtained from the clinic chart. The mean ± SD number of HbA_1c values per participant was 2.9 ± 1.3 in the excellent control group and 2.6 ± 1.3 in the fair/poor control group. Severe hypoglycemia (SH) was defined as the occurrence of hypoglycemia-induced seizure or loss of consciousness. Diabetic ketoacidosis (DKA) was defined as the occurrence of ketoacidosis that resulted in overnight hospitalization.

Characteristics between the excellent control versus fair/poor control groups were compared by t test for continuous variables and χ² test for categorical variables (Mantel-Haenszel statistics for ordered categories). Separate analyses were conducted for insulin pump and injection users. Analyses initially were conducted in four age-groups (26–<31, 31–<50, 50–<65, and ≥65 years) but then pooled across age-groups because results among the age-groups appeared similar. In view of the large sample size and number of variables evaluated, only P < 0.01 was considered to be meaningful. SAS version 9.3 (SAS Institute, Cary, NC) was used for the analyses.

The characteristics of the 627 participants with excellent control and 1,267 with fair/poor control are shown in Table 1. Compared with the fair/poor control group, the excellent control group on average was 2.6 years older; less likely to have a BMI in the overweight or obese range; more likely to be white non-Hispanic; more likely to have a higher income, higher education level, and private insurance; and more likely to be married (P < 0.0001 for each). Duration of diabetes was similar in the two groups. In the excellent control group, 336 (54%) were using an insulin pump compared with 580 (46%) in the fair/poor control group (P = 0.001).

A number of factors related to diabetes management differed significantly (P < 0.0001) between the excellent control and fair/poor control groups (Table 2), with similar findings among both pump and injection users (Supplementary Tables 1–3). Those in the excellent control group more frequently performed self-monitoring of blood glucose (SMBG) (72 vs. 36% reporting SMBG frequency ≥5 times/day), including more frequent SMBG measurements before giving a bolus (56 vs. 32% reporting always doing this); less frequently missed insulin doses (94 vs. 55% reporting missing a dose <1/week); more often gave a mealtime insulin bolus before a meal rather than at the time of or after a meal (69 vs. 54%); and more frequently exercised ≥3 days/week (72 vs. 59%). In both pump and injection users, the average total daily insulin dose was lower in the excellent control group than in the fair/poor control group (P < 0.0001), and the ratio of bolus to basal insulin was higher (P = 0.001). A comparison of the excellent and fair/poor control groups on diabetes management factors is shown in Table 2. At least three of the four key aspects of diabetes management (SMBG ≥5 times/day, always performing SMBG before giving a bolus, giving a meal bolus before the meal, and missing an insulin dose <1 time/week) were reported by 62% of the excellent group and 26% of the fair/poor group (P < 0.0001).

Among pump users (Supplementary Table 2), the excellent control group tended to have a greater number of basal insulin rate changes per day (3.9 ± 2.1 vs. 3.4 ± 2.0, P = 0.001); average duration of pump insertion was similar in the excellent and fair/poor control groups (3.3 ± 0.7 vs. 3.3 ± 0.8 days, P = 0.2). Among injection users (Supplementary Table 3), most participants in both the excellent and the fair/poor control groups were using a regimen that included short- and long-acting insulins.

Hypoglycemia-induced seizure or loss of consciousness within the prior 12 months was reported by 13% of the excellent control and 12% of the fair/poor control groups (P = 0.7). DKA was reported by 1 and 12%, respectively (P < 0.0001). Sixty-two percent of the excellent control group described their general health as very good or excellent compared with 21% of the fair/poor control group (P < 0.0001). Fifty percent of the excellent control group reported that they never or rarely felt stress about their diabetes compared with 27% of the fair/poor control group (P < 0.0001).

Analysis of the large T1D Exchange clinic registry database provided the opportunity to gain a better understanding of why some adults with type 1 diabetes achieve better glycemic control than others. Some of the differentiating features indirectly contributed, such as income, education level, health insurance, and marital status, mostly indicators of higher socioeconomic status that are likely not modifiable. This association with socioeconomic status has been demonstrated in pediatric patients but has not been well studied in adult populations (4,5). Because potentially modifiable factors associated with glycemic control are of the most interest, we intentionally did not adjust for socioeconomic status in evaluating differentiating aspects of diabetes management. We only considered P < 0.01 to be significant in view of the multiple factors evaluated, and almost all significant associations had a P < 0.0001, reflecting the large sample size. Although it seems unlikely that differential reporting between groups would account for the significant differences found, it is possible that some of the differences could be underestimates if participants in the fair/poor control group misreported some of the information more often than those in the excellent control group, such as frequency of missed insulin doses.

Although for all diabetes management factors there was overlap between the excellent and fair/poor control groups, several factors stood out as tending to differentiate the two groups, particularly frequency of SMBG measurements, frequency of missing an insulin dose, and timing of the meal bolus. An association between SMBG frequency and HbA_1c has been shown in other studies (6–9). The finding related to timing of the meal bolus is consistent with findings in patients with type 1 diabetes describing lower glycemic excursions when insulin is given 20 min before a meal compared with immediately before or 20 min after a meal (10); however, a randomized crossover study in type 2 diabetes did not find a beneficial effect of giving an early bolus before a meal on HbA_1c (11). The observational nature of the present study precludes a definitive statement regarding causality. Nevertheless, it is important for insurers to consider that reducing restrictions on the number of test strips provided per month may lead to improved glycemic control for some patients with type 1 diabetes, resulting in a potential cost-savings from both short- and long-term complications.

Of note, participants with excellent HbA_1c values had lower BMIs, exercised more frequently, and had lower total daily insulin dose per kilogram. Although it is not possible to establish a causal relationship, exercise improves insulin sensitivity (12), as does lowering BMI (13). The fact that total daily insulin doses also were lower suggests that there may be a degree of insulin resistance in those with the higher HbA_1c levels that could be affected by an increase in exercise and weight loss. Additionally, participants with excellent control were more likely to report an improved sense of overall health as well as lack of stress about diabetes. Whether these findings are because of a sense of self-efficacy resulting in improved diabetes management or whether the improved perception of health is related to better diabetes control is difficult to determine. If improved perception of health leads to improved health, then perhaps counseling and educational programs can be important components of diabetes management.

The lack of an increase in SH in patients with excellent control compared with those with fair/poor control is reassuring in knowing that a low HbA_1c level can be achieved with a risk for SH that is no higher than the risk in those with fair/poor control. This finding differs from DCCT findings in which there was a strong association between lower HbA_1c levels as a result of intensive management and an increase in SH (1). However, but the finding is consistent with a more recent study (14) that did not demonstrate an association between lower HbA_1c and frequency of SH episodes. This may be due to an improvement in insulin management through the use of short-acting insulin analogs or diabetes education, resulting in appropriate adjustment of insulin doses with mild hypoglycemia. In contrast, the frequency of DKA, not surprisingly, was higher in the fair/poor control group.

In conclusion, diabetes self-management related to insulin delivery, glucose monitoring, and lifestyle tends to differ when comparing adults with type 1 diabetes under excellent control with those under poorer control. A better understanding of the aspects of diabetes self-management associated with better glycemic control on the part of patients may lead to improved control and better long-term outcomes with lower risk of microvascular and macrovascular complications. Future studies should focus on modification of diabetes management skills in adult patients with type 1 diabetes who have suboptimal glycemic control.

Funding was provided by the Leona M. and Harry B. Helmsley Charitable Trust.

R.M.B. has served on a scientific advisory board and consulted or performed clinical research with Abbott Diabetes Care, Amylin, Bayer, Becton Dickinson, Boehringer Ingelheim, Intuity, Calibra, Dexcom, Eli Lilly, Halozyme, Helmsley Trust, Hygieia, Johnson & Johnson, Medtronic, Merck, National Institutes of Health, Novo Nordisk, ResMed, Roche, Sanofi, and Takeda. His employer, Park Nicollet, has contracts with the listed companies for his services, and no personal income goes to R.M.B. He has inherited Merck stock and has been a volunteer officer of the American Diabetes Association. D.M.H. serves as a board member for Grove Instruments. J.F.L. has received consultancy fees from Dexcom and Valeritas. R.W.B.’s nonprofit employer has received consultant payments on his behalf from Sanofi and Animas and a research grant from Novo Nordisk with no personal compensation to R.W.B. No other potential conflicts of interest relevant to this article were reported.

J.H.S., V.C., K.M.M., and J.B.M. researched data, contributed to the discussion, and wrote the manuscript. R.M.B., R.S.G., D.M.H., J.F.L., and E.M.M. contributed to the discussion and reviewed and edited the manuscript. R.W.B. researched data, contributed to the discussion, and reviewed and edited the manuscript. R.W.B. is the guarantor of this work and, as such, had full access to all the data in the study and takes responsibility for the integrity of the data and accuracy of the data analysis.