Non-invasive markers of autonomic regulation in response to normal daily activities in health and cardiovascular disease

With the recognition of autonomic nervous dysregulation in the development and progression of cardiovascular diseases, such as hypertension, obesity, sleep apnoea, and heart failure, non-invasive markers of autonomic function have been widely used to predict cardiovascular risks. Short term recordings (5-10minutes) of ECG and beat-to-beat finger blood pressure are easily accessible, and carry rich information on how the sympathetic and parasympathetic nerve systems modulate the heart and blood vessels. Power spectral analysis of heart rate and blood pressure variability is a well-established tool in evaluating the sympathetic and vagal modulation. The present study investigated the autonomic responses to normal daily activities using a novel experimental protocol to mimic a common behaviour in western societies – assuming upright posture after eating. The study revealed an enhanced sympathetic activation to orthostatic stress in the postprandial state (within two hours after meal ingestion) with associated pressor and tachycardiac responses in healthy young men. In older subjects, we find a higher basal sympathetic tone, and an attenuated autonomic response to orthostatic stress and meal ingestion; interestingly, meal ingestion induced distinct sympathetic and vagal responses between older men and women, suggesting an additional factor that may increase the risk of cardiovascular diseases in postmenopausal women.Vascular dysregulation may underlie the pathogenesis of open angle glaucoma, regardless of an increase in intraocular pressure (i.e. high tension glaucoma and normal tension glaucoma). The main study, using the above experimental protocol and approaches, demonstrates for the first time a systemic autonomic dysfunction in both high tension glaucoma and normal tension glaucoma patients, and that the two forms of glaucoma manifest distinct features in autonomic responses. The study provides new evidence that open angle glaucoma may be a systemic cardiovascular autonomic disorder, and glaucomatous visual defects may be an early clinical manifestation of the continuum of multiple target organ damage later in life.