Abbreviation
WMHs white matter hyperintensitiesTo the Editor: We appreciate the valuable comments of Dr Wessels [1] on our recent article in Diabetologia [2]. We specifically sought to study the impact of white matter hyperintensities (WMHs) on brain structure in relatively young patients (age 32±4 years) with diabetes of long duration (20±4 years) (mean ± SD). As Wessels noted, our large sample of patients did not differ from non-diabetic controls in terms of severity of white matter lesions. Indeed, our results are similar to those of Brands et al. [3], who studied cognition and WMHs in older type 1 diabetic adults with disease of longer duration associated with more complications. Taken together, these studies suggest that the incidence of WMHs in type 1 diabetes is not likely to be high. Using voxel-based morphometry, we have also found that, compared with non-diabetic controls, patients with type 1 diabetes had lower grey matter density and this was associated with both higher HbA 1c levels and an increased number of severe hypoglycaemic events [4]. This finding suggests that more sensitive measures of brain structure would reveal changes induced by type 1 diabetes.Wessels notes that type 1 diabetes leads to changes in cognition, which may be mediated by hyperglycaemia, hypoglycaemia and/or vascular disease. The literature on these points is far from conclusive. We observed only small differences in cognition when comparing type 1 diabetic patients to non-diabetic controls [2]. Our results are consistent with a meta-analysis that found modest effects of type 1 diabetes on cognition, characterised by slowing of mental processing and diminished mental flexibility [5]. Furthermore, our cognitive data were consistent with recent results from an 18 year longitudinal study of type 1 diabetic patients enrolled in the Diabetes Control and Complications Trial [6], which found only minimal changes in psychomotor efficiency and motor speed over time among those with the highest HbA 1c levels.Wessels' suggestion that we examine our WMH findings in relation to total white matter volume measurements in patients with and without retinopathy is of interest and would be a useful complementary design. Our goal is to utilise multiple methods of assessing the grey and white matter compartments of the brain, to develop a more precise understanding of the 'signature' of type 1 diabetes. Diabetologia