Early autonomic dysfunction in type 1 diabetes: a reversible disorder?

Abstract

Aims/hypothesis Cardiac autonomic neuropathy is associated with increased morbidity and mortality rates in patients with type 1 diabetes. The prevalence of early autonomic abnormalities is relatively high compared with the frequency of manifest clinical abnormalities. Thus, early autonomic dysfunction could to some extent be functional and might lead to an organic disease in a subgroup of patients only. If this is true, manoeuvres such as slow deep-breathing, which can improve baroreflex sensitivity (BRS) in normal but not in denervated hearts, could also modify autonomic modulation in patients with type 1 diabetes, despite autonomic dysfunction.Methods We compared 116 type 1 diabetic patients with 36 matched healthy control participants and 12 hearttransplanted participants with surgically denervated hearts. Autonomic function tests and spectral analysis of heart rate and blood pressure variability were performed. BRS was estimated by four methods during controlled (15 breaths per minute) and slow deep-breathing (six breaths per minute), and in supine and standing positions. Results Conventional autonomic function tests were normal, but resting spectral variables and BRS were reduced during normal controlled breathing in patients with type 1 diabetes. However, slow deep-breathing improved BRS in patients with type 1 diabetes, but not in patients with surgically denervated hearts. Standing induced similar reductions in BRS in diabetic and control participants. Conclusions/interpretation Although we found signs of increased sympathetic activity in patients with type 1 diabetes, we also observed a near normalisation of BRS with a simple functional test, indicating that early autonomic derangements are to a large extent functional and potentially correctable by appropriate interventions.

Deep breathing improves blunted baroreflex sensitivity even after 30 years of type 1 diabetes

“…As none of the methods has been proved to be superior to the others, we used a set of four different tests and present the BRS data as the average of these methods. This proved to be a more robust estimate than the use of single tests [7,23].…”

“…Diabetic neuropathy has conventionally been considered to be an irreversible, organic process [6]. However, in a previous study we demonstrated that, in patients with type 1 diabetes and early autonomic impairment as indicated by reduced baroreflex sensitivity (BRS), the BRS was in fact normalised during slow breathing [7]. The importance of this finding lies in the fact that reduced BRS is an established marker of poor prognosis in cardiovascular medicine [8][9][10], and also an early marker of autonomic alteration in diabetes [11][12][13].…”

“…The data from the patients with a long duration of type 1 diabetes were compared with previously published data on patients with a short duration of type 1 diabetes (n=117, diabetes duration 8.9±0.1 years), an age-and sex-matched control group (n=36) and a group of heart-transplanted participants (n=12) [7]. The group of heart-transplanted individuals served as a model of definitive denervation in the figures, and the data were not used in the statistical analyses.…”

“…Spectral analysis of heart rate and blood pressure variability and assessment of the BRS Data acquisition and analysis was performed as previously described [7]. ECG and continuous blood pressure were recorded in the supine position during 5 min of spontaneous breathing, 5 min of controlled breathing (15 breaths per min) and 1 min of slow deep breathing (six breaths per min).…”

Complexity of Impaired Parasympathetic Heart Rate Regulation in Diabetes

“…Much like in diabetic Akita mice, functional and potentially reversible reductions in parasympathetic heart rate control can occur in human beings. More detailed physiologic (14) or pharmacologic (15) tests may be required to differentiate functional and structural parasympathetic dysfunction in diabetic patients. Furthermore, the cause of the change in parasympathetic heart rate control is difficult to localize.…”