Mean HbA1c over 18 years predicts carotid intima media thickness in women with type 1 diabetes

Aims/hypothesis Intima media thickness (IMT) of the common carotid artery (CCA) is a validated surrogate marker of early atherosclerosis. The aim of our study was to assess the association between IMT in CCA and long-term mean HbA₁c in type 1 diabetes. We also elucidated the association between carotid IMT and preclinical coronary atherosclerosis.Methods In 39 individuals with type 1 diabetes, HbA₁c was measured prospectively over 18 years. The IMT examinations were performed with high-resolution ultrasound. The association between carotid IMT and preclinical coronary atherosclerosis (assessed by intravascular ultrasound [IVUS]) was tested in 29 of the patients.Results Mean HbA₁c over 18 years was 8.2% (range: 6.6–11.3%). Mean age at follow-up after 18 years was 43 years and mean duration of diabetes was 30 years. IMT was significantly higher in diabetic patients than in an age- and sex-matched reference population. The IMT values were at the same level as for controls who were 20 years older. In women, HbA₁c was significantly associated with mean average CCA IMT (r²=0.77, p<0.0001 when adjusted for age), whereas there was no significant association for men. Among women, a significant association was also found between carotid IMT and the percentage of coronary vessel area stenosis (r=0.65, p=0.03).Conclusions/interpretation The present findings suggest an important role of long-term hyperglycaemia in the development of atherosclerosis, especially in women with type 1 diabetes.Type 1 diabetes patients have earlier development of, and more advanced, atherosclerosis compared with an age- and sex-matched reference population. In women, carotid IMT reflects preclinical coronary atherosclerosis.