Determinants of HbA1c in non-diabetic children and adults

HbA1c has been firmly established as an index of long term glucose concentrations and as a measure of the risk for the development of complications in patients with diabetes mellitus. Recently, an international expert committee recommended using HbA1c as indicator for diagnosing diabetes. Consequently, an increased use of HbA1c can be expected. Therefore, it is important to get better insight in the normal distribution of HbA1c in non-diabetic children of all ages and to increase the knowledge about all the factors determining HbA1c in non-diabetic persons from childhood onwards. The main aim of this thesis is to investigate determinants of HbA1c in non-diabetic children and adults. We investigated the distribution and determinants of HbA1c in non-diabetic infants aged 8-12 months and non-diabetic children aged 8-9 years. In addition, we investigated lifestyle determinants of HbA1c at age 12 years and the effects of growth on change in HbA1c between the age of 8 and 12 years, and we investigated the effect of environmental factors, genetic factors and gene-environment interactions on HbA1c in non-diabetic adults. From these studies we conclude that: 1. HbA1c is normally distributed in non-diabetic infants and children; 2. Known risk factors for type 2 diabetes are not associated with HbA1c in non-diabetic infants and children; 3. HbA1c in non-diabetic children is fairly stable over time; 4. A substantial part of HbA1c is determined by other factors besides glycaemia and erythrocyte lifespan. And therefore we conclude in the general discussion that HbA1c is not suitable for diagnosing diabetes.