The most important finding of the present study is that HbA1c obtained during the first year after diagnosis of disease is inversely correlated to certain subscales of QoL of patients with T1DM at Tstudy, i.e. some 5 years after disease onset. Our results are therefore in line with previous studies in which good metabolic control was shown to be associated with better QoL (3). The ratings of parents and children differed from each other significantly as already found by Hoey et al. (3, 4) enforcing the importance of separate ratings.
In previous studies, HbA1c was measured at time of study inclusion, e.g. more than 5 years after diagnosis (3), whereas in the present study, HbA1c was obtained during the first year after diagnosis of disease. The development of HbA1c from onset of T1DM over a year was found to be associated with QoL at Tstudy, i.e. 4.9 (3.6) years after onset. When HbA1c was higher in the first year, patients reported significantly lower QoL on average 4 years later. These results concur with HbA1c being a potential predictor of QoL. The adjustment of metabolic control reflected by HbA1c from onset of T1DM obviously has an impact on the well-being of the children later on. Importantly, patients indicated lower self-esteem. As low self-esteem is associated with psychiatric disorders such as depression or substance use (22, 23), children with T1DM might need close follow-up.
The development of HbA1c after disease onset varied during the observational period. HbA1c was highest at T0. At T6 the decline in HbA1c is probably due to a more rigorous adjustment of metabolic control. Later on, the motivation of children is likely to be reduced as indicated by an increase in HbA1c at T12. This underlines the importance to keep the focus on good metabolic control and on the acceptance of the disease in order to enhance QoL also later on.
With respect to HbA1c (Tstudy), the QoL ratings of parents and patients differed. Children with higher HbA1c values rated themselves lower on overall QoL especially on the subscale of self-esteem whereas parents perceived lower QoL of their child on the subscales of friends and school. This is an important issue for diabetes management because the different perceptions of patients and parents may call for the need of tailored support in order to discover problem fields and to maximize QoL.
The final part of the study was to measure fitness level and electrophysiological abnormalities in children with T1DM. As patients and controls did not differ significantly in the results of the 6MWT the subjects were presumably on average at the same fitness level. This is in contrast to previously published findings of reduced fitness in children with T1DM (15). Notably, only children with poor metabolic control showed alterations in aerobic an anaerobic muscle functions (16).
For electrodiagnostic parameters, a detailed neurophysiological examination of children with T1DM compared to healthy children was performed. There were no electrophysiological abnormalities in patients with T1DM compared to control group, except for a significantly slowed median motor NCV. Additionally, no correlation between NCVs and HbA1c was found at any point in time. This is in contrast to other studies reporting frequent subclinical neuropathy in diabetic children (13, 14). Notably, mean disease duration was considerably longer in previous studies, exceeding seven years (14). Diabetic polyneuropathy did therefore likely not occur at this early stage of disease in the present study. Nerve conduction studies are the gold standard for the detection of subclinical neuropathy and determining neurophysiological measurements (15). Measuring NCVs in children is a big challenge, which renders it often difficult to find differences in T1DM patients. Due to artefacts and limited compliance of the children, a supramaximal stimulation was not always ensured in our study. Potentially, more suitable screening tools such as vibration sensation thresholds and thermal discrimination thresholds that are quicker and easier in the implementation might be more appropriate for use in studies of children (14).