Autonomic dysfunction associated with Type 1 diabetes: a role for fitness?

Excerpt

A robust and highly responsive autonomic nervous system (ANS) is an invaluable component to human health. The ANS innervates and governs most human organ systems via its two subdivisions, the sympathetic and parasympathetic nerves. For example, patients with differing levels of ANS dysfunction can present with impairments in blood pressure regulation, control of heart rate, and thermoregulation to name a few [6]. While changes in autonomic control have been linked to several chronic diseases and disorders, the large fluctuations in blood glucose levels associated with Type 1 diabetes mellitus (T1DM) tend to place these patients at particularly greater risk [3]. The impairment in ANS function associated with T1DM has been noted in numerous studies, even in those patients who appear to be otherwise “healthy” (i.e., no diagnosed retinopathy, nephropathy, or clinical neuropathy) [11, 12]. A recently published study by Limberg et al. [8] not only eloquently highlights how ANS function is impaired in patients with T1DM at rest, but also how factors as simple as glycemic management can exacerbate impairments in autonomic control. Specifically, these findings were evidenced by marked reductions in heart rate variability, spontaneous cardiac baroreflex sensitivity, and T-wave amplitude along with prolonged QT intervals during and following an acute hypoglycemic episode [8]. Considering that ~82 % of patients with T1DM report at least 1 hypoglycemic event each month [4], with greater frequencies reported during physically demanding tasks or physical exercise [14], implementing interventions which can delay and/or reverse ANS dysfunction in these patients is paramount. …