Our findings documented significant deterioration in glycemic control over a 2-year period as youth with type 1 diabetes transition to adolescence. Treatment adherence defined as BGMF, which also deteriorated over the course of the study period, demonstrated a robust effect on change in glycemic control after controlling for clinically relevant covariates. Specifically, one less check of blood glucose per day across this 2-year period predicted an increase in HbA1c of 1.26% (e.g., 8.0–9.26%). The clinical significance of this finding is difficult to ascertain.
Although the influence of treatment adherence on glycemic control has been relatively well documented in older adolescents (3
), our findings document the substantial impact of declining adherence on subsequent glycemic control for youth with type 1 diabetes whose baseline glycemic control data were obtained at the onset of adolescence. These data suggest that the magnitude of the effect of declining BGMF on glycemic control in young adolescents may be even greater than declines observed among older adolescents. Early adolescence may represent a critical transition period in treatment adherence for which targeting preventive intervention should be targeted toward preserving BGMF and thus altering the potential trajectory of increased and suboptimal glycemic control. Our results are consistent with Driscoll et al. (18
), who found that BGMF increased before clinic visits for children with lower HbA1c
The absence of a bidirectional effect of glycemic control on treatment adherence also has useful clinical implications for clinical assessment and treatment planning. The findings affirm the observation that glycemic control is not a valid proxy for treatment adherence (19
). In other words, the clinician who obtains an above-target HbA1c
value for a particular patient and family and then assumes poor treatment adherence may miss other relevant contributors to glycemic control such as dosing, timing of insulin administration, and variability and frequency of BGM. This clinical management strategy may also have the unintended effect of demotivating patients and families, especially if they have been trying to adhere to treatment recommendations but still have an above-target HbA1c
. Alternatively, data from this study suggest that readily available data concerning treatment adherence (e.g., number of daily blood glucose checks) does predict glycemic control and can be used as a primary method to guide targeted clinical management. In particular, those youth who demonstrate a decreasing BGMF during early adolescence can be targeted for intensive interventions to increase their BGMF.
Several limitations should be considered when interpreting our findings. Although the homogeneity in ages of our sample is a strength because of its developmental specificity, it also limits the generalizability of our findings, as does the sample demographics that included a majority of white and more educated families. In addition, the findings were limited to a 2-year follow-up. We also used BGMF as an indicator of treatment adherence. Although there is substantial support for this objective measure of treatment adherence in pediatric type 1 diabetes (17
), BGMF may not fully capture the multidimensional nature of treatment adherence. However, our experience suggests that youth and families in this age group who are not checking as frequently as is prescribed are also not fully engaging in other adherence behaviors, due to lack of blood glucose data to make necessary changes in insulin or to other variables such as insufficient diabetes knowledge, support, or motivation. Finally, adherence is one of a number of variables (e.g., the well-documented (7
) effect of hormonal changes during the onset of puberty) that can influence glycemic control. In the current study, pubertal status at baseline was associated with changes in glycemic control, but this effect was controlled for in our analysis. However, the absence of a bidirectional effect of glycemic control on treatment adherence may reflect the influence of puberty.
Future research should address these limitations by studying broader, more representative samples across a more extended period of time. Our subsequent analyses will describe prediction of change in glycemic control over 3 years when prospective data collection is complete. The present findings might be extended to identify subgroups of adolescents with differing trajectories of glycemic control and clarify how individual differences in trajectories of treatment adherence map onto glycemic control. The frequency of BGM, which is readily available to practitioners in their routine care of adolescents with type 1 diabetes, offers a powerful tool for targeted management of type 1 diabetes, especially when combined with data concerning recent trajectories of glycemic control.