Cerebral haemodynamics, cognition and brain volumes in patients with type 2 diabetes

Background: Type 2 diabetes mellitus (T2DM) is associated with cognitive impairment and brain abnormalities on MRI. The underlying mechanisms are unclear. We examined the relationship between cerebral haemodynamics (cerebral blood flow (CBF) and cerebrovascular reactivity (CVR)) and cognitive performance and brain volumes in patients with T2DM, at baseline and after four years. Methods: 114 patients with T2DM, aged 56-80 years, underwent a detailed cognitive assessment and MRI scan. In 68 patients the evaluation was repeated after four years. CBF (two-dimensional flow-encoded phase-contrast MRI) and CVR (carbogen breathing response middle cerebral artery; transcranial Doppler) were measured at baseline. Cognitive performance was expressed as composite z-score and regression based index score. Brain volumes were measured on MRI by automated segmentation. The relationship of haemodynamics with cognition and brain volumes was examined with linear regression analyses adjusted for age, sex and IQ. Results: Mean CVR was 51.8% +/- 18.0% and mean rCBF 53.3 +/- 11.3 ml/min/100 ml brain tissue. CBF was associated with baseline cognitive performance (standardized regression coefficient beta (95% CI): 0.17 (0.00; 0.32) and total brain volume (0.23 (0.05; 0.41)). No correlation was found between CVR and baseline cognitive performance. Neither CBF nor CVR predicted change in cognition (CBF 0.11 (-0.21: 0.44); CVR 0.07 (-0.21: 0.36)) or total brain volume (CBF 0.09 (-0.22: 0.39); CVR 0.13 (-0.13; 0.40)) over four years. Conclusions: CBF was associated with impaired cognition and total brain volume in cross-sectional analyses, but did not predict changes in cognition or brain volumes over time. Apparently, alterations in cerebral haemodynamics play no major etiological role in cognitive decline or change in brain volumes in non-demented individuals with T2DM. (c) 2012 Elsevier Inc. All rights reserved.