Is the relationship between adherence behaviours and glycaemic control bi-directional at adolescence? A longitudinal cohort study.

Aim: To analyse the change in adherence to diabetes treatment and its association with metabolic control from childhood to adolescence. The Tanner pubertal staging model was selected as a marker of developmental maturity.

Methods: In a multicentre, longitudinal cohort study, 142 children with Type 1 diabetes completed a scale that assessed adherence to treatment and a test of diabetes knowledge at the beginning of the study (T0) and four years later (T4). HbA1c and clinical data were collected at T0 and at T4.

Results: From T0 to T4, the mean HbA1c increased from 8.2 +/- 1.6 to 9.1 +/- 1.4% (P < 0.001). Among patients at pubertal stages 1-4, adherence did not decline from T0 to T4, whereas the HbA1c level increased and a positive correlation between adherence and the knowledge score was noted (r = 0.32; P < 0.02). Among adolescents at pubertal stage 5, the level of adherence decreased (P < 0.01) from T0 to T4 and the HbA1c level increased despite an increase in the knowledge score (P < 0.001), a negative correlation between HbA1c and adherence was found (r = -0.37; P = 0.001) and adherence at T4 significantly added to the prediction of HbA1c at T4.

Conclusions: In this longitudinal study, an initial worsening of glycaemic control as a result of puberty preceded worsening of adherence behaviours. Low levels of adherence become predictive of HbA1c degradation among pubertal stage 5 adolescents. These results suggest a potential bi-directional relationship between glycaemic control and adherence.