Abstract
Background: Autonomic function has received little attention in Alzheimer’s
disease (AD). AD pathology has an impact on brain regions which are important for central
autonomic control, but it is unclear if AD is associated with disturbance of autonomic
function.
Objective: To investigate autonomic function using standardized techniques in
patients with AD and healthy age-matched controls.
Method: Thirty-three patients with mild to moderate AD and 30 age- and
gender-matched healthy controls, without symptoms of autonomic dysfunction, underwent
standardized autonomic testing with deep breathing, Valsalva maneuver, head-up tilt, and
isometric handgrip test. Brachial pressure curve and electrocardiogram were recorded for
off-line analysis of blood pressure and beat-to-beat heart rate (HR).
Results: AD patients had impaired blood pressure responses to Vasalva
maneuver (p < 0.0001) and HR response to isometric contraction
(p = 0.0001). A modified composite autonomic scoring scale showed
greater degree of autonomic impairment in patients compared to controls (patient:
2.1 ± 1.6; controls: 0.9 ± 1.1, p = 0.001). HR response to deep breathing
and Valsalva ratio were similar in the two groups.
Conclusion: We identified autonomic impairment ranging from mild to severe in
patients with mild to moderate AD, who did not report autonomic symptoms. Autonomic
impairment was mainly related to impairment of sympathetic function and evident by
impaired blood pressure response to the Vasalva maneuver. The clinical implications of
this finding are that AD may be associated with autonomic disturbances, but patients with
AD may rarely report symptoms of autonomic dysfunction. Future research should
systematically evaluate symptoms of autonomic function and characterize risk factors
associated with autonomic dysfunction.
