Abstract
Introduction: Vascular brain changes and risk factors play a role in development and progression of Alzheimer's disease (AD). The primary aim of our study was to determine the predictive value of neurosonological biomarkers of cerebral microvasculature resistance index (RI) and breath-holding index (BHI) for the development AD dementia in the older non-demented population.
The secondary aim was to compare RI and BHI with other vascular bio markers. Methods: A prospective study with patients with mild cognitive impairment (MCI), subjective memory complaints (SCD) and AD dementia patients as controls.
All subjects underwent a detailed neuropsychology examination, brain magnetic resonance imaging and transcranial colour-coded sonography, including the evaluation of BHI and RI in the middle cerebral artery (MCA). Results: One hundred and eighty-three patients were enrol led, of which 113 patients with a diagnosis of MCI (n = 38), SCD (n = 49) and AD (n = 26) were included in the analysis.
During the follow-up period (mean 40 months), 23 (26.4%) patients converted to dementia. Patients in the conversion group had a significantly lower BHI for both hemispheres; there was no significant difference in the RI values.
The ROC analysis showed the cut-off values of BHI = 0.50 for left and BHI = 0.57 for right MCA (Z-score BHI < 0) to be the best predictive factors for dementia conversion. The hazard ratio (HR) of AD conversion for Z-score BHI < 0 was 5.61 (95% CI 1.66-18.97).
The patients with conversion also had a significantly higher age, lower body mass index, higher frequency of ischaemic heart disease, APOE epsilon 4 allele and more severe hippocampal atrophy and vascular white matter lesions. Conclusion: BHI measurement seems to be the most useful neurosonological marker of AD conversion.
In our study, BHI = 0.50 for left MCA and BHI = 0.57 for right MCA show the best predictive value for conversion to AD dementia.