QT dispersion and heart rate variability abnormalities in Alzheimer's disease and in mild cognitive impairment

OBJECTIVES: To investigate the effect of cardiovascular changes (i.e., QT interval, QT dispersion (QTD), heart rate variability (HRV), and other cardiovascular measures) in subjects with Alzheimer's disease (AD) and mild cognitive impairment (MCI). DESIGN: Each subject underwent clinical and cognitive examination, a structural brain imaging study, echocardio-Doppler, electrocardiogram (ECG), HRV analysis using 24-hour ECG monitoring, and 24-hour blood pressure monitoring. SETTING: Community population-based sample of patients admitted to an AD center for investigation of cognitive disturbances. PARTICIPANTS: Thirty-three subjects with AD, 39 subjects with MCI, and 29 cognitive healthy subjects (controls) matched for demographic characteristics, hypertensive condition, smoking habits, and laboratory parameters were enrolled consecutively. MEASUREMENTS: Clinical and cognitive examination, structural brain imaging study, echocardio-Doppler, ECG, HRV analysis using 24-hour ECG monitoring, and 24-hour blood pressure monitoring. RESULTS: QTD and QT corrected dispersion mean values were significantly higher in patients with AD than in patients with MCI and controls and higher in patients with MCI than in controls. HRV time and domain parameters were lower in patients with AD than in patients with MCI and controls. No difference in other cardiovascular measures was found. QTD and HRV were found to be significantly correlated with the degree of cognitive impairment. CONCLUSION: These findings support the presence of a peculiar neuroanatomic dysfunction in patients with AD and MCI that parallels the disease progression. These non-invasive parameters might prove to be powerful predictive tools in the worsening of cognitive function and mortality risk.