Autonomic function in Alzheimer: assessment using tilt-table testing

There are indications that autonomic function is affected in patients with
Alzheimer. To investigate autonomic function in Alzheimer, prolonged head-up
tilt-table testing (HUTT) will be applied. During HUTT the autonomic nervous
system is challenged, specifically baroreflex function. Cardiovascular and
cerebrovascular signals will be measured to determine autonomic control of
heart rate and blood pressure (BP) and to determine the effect of any changes
in BP on cerebral blood flow. These signals include continuous BP,
electrocardiography (ECG), transcranial doppler (TCD) and near-infrared
spectroscopy (NIRS). It has been hypothesized that AD is associated with
autonomic dysfunction. We will investigate this in patients with symptomatic
Alzheimer*s disease, i.e. in patients with Mild Cognitive Impairment (MCI) and
Alzheimer*s Disease dementia (AD). In addition to traditional linear analyses,
complexity analyses will be explored in this study. Due to the complex
intertwined underlying physiological processes, looking at complexity analyses
instead of traditional linear measures, such as mean and standard deviation,
could result in innovative ways to assess impaired autonomic function.

The primary objective is to determine if there is a difference in autonomic
function between patients with Alzheimer*s disease (MCI and AD) and a matched
control group. The secondary objectives will be explorative and aimed to
investigate cardiovascular and cerebrovascular complexity measures in patients
with MCI and AD. Other objectives will be to determine the added value of
complexity measures compared to traditional linear measures, such as the mean
and standard deviation.

Explorative study to assess cardiovascular and cerebrovascular parameters in
MCI and AD as measures of autonomic function during prolonged HUTT.

All measurement techniques and test procedures are non-invasive. Individuals
can only feel discomfort due to presyncope symptoms. All participants will be
asked to visit the lab once. This places only a minor burden on participants.
There will be no direct benefits for participants, with the exception that a
finding of autonomic impairment could result in medical advice to the general
practitioner and/or geriatrician. The knowledge obtained in this study will
contribute to a better understanding of autonomic function in AD, which can
translate into knowledge about the risks of dizziness and syncope in this
population, and inform the treatment of cardiovascular diseases (e.g.
hypertension) in this population. The knowledge obtained will also contribute
to our understanding of AD, which is a complex, multicausal disease.