Autonomic dysfunction in type 2 diabetes mellitus with and without vascular dementia

Autonomic dysfunction has been implicated in sudden cardiac death and cognitive impairment in diabetes.

Objectives of the study were to examine the associations between vascular, metabolic risk factors, autonomic and cognitive function in patients with diabetes mellitus.

We investigate autonomic function in 45 participants with type 2 diabetes and in 23 age related normal subjects, using Ewing's tests and power spectral analysis of heart rate variability. Mini Mental State Examination and Hachinski's ischemic scale were used to identify vascular dementia. Only 11 patients were diagnosed with vascular dementia.

The glycosylated haemoglobin, triglycerides, and systolic blood pressure had much larger values in vascular dementia patients compared to the controls. The averages of results obtained in heart rate deep-breathing, Valsalva ratio and lying-to-standing tests for vascular dementia patients are statistically lower than the averages for controls. Vascular dementia patients had a greater fall in blood pressure on standing (p<0.001) and reduced blood pressure responses to isometric exercise (p<0.001) in comparison with controls. Also they had an increase in the mean heart rate at rest (p<0.05), a decrease in time domain parameters of heart rate variability (p<0.001), and an increase in the low/high frequency component ratio (p<0.001) indicating a vagal-sympathetic dysfunction.

Using standard cardiovascular reflex tests and analysis of heart rate variability we demonstrated an impairment of the autonomic nervous system in vascular dementia patients with marked parasympathetic dysfunction and sympathetic predominance.