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). HbA(1c) and clinical data were collected at T0 and at T4. Results From T0 to T4, the mean HbA(1c) 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 HbA(1c) 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 HbA(1c) level increased despite an increase in the knowledge score (P < 0.001), a negative correlation between HbA(1c) and adherence was found (r = -0.37; P = 0.001) and adherence at T4 significantly added to the prediction of HbA(1c) 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 HbA(1c) degradation among pubertal stage 5 adolescents. These results suggest a potential bi-directional relationship between glycaemic control and adherence.