How does poor glycemic control affect the autonomic nervous system (ANS)?

From the Guidelines

Poor glycemic control significantly impairs the autonomic nervous system by causing diabetic autonomic neuropathy, which can lead to increased morbidity, mortality, and decreased quality of life. According to the most recent and highest quality study 1, autonomic neuropathy can increase the risk of exercise-induced injury or adverse events through decreased cardiac responsiveness to exercise, postural hypotension, impaired thermoregulation, impaired night vision due to impaired papillary reaction, and greater susceptibility to hypoglycemia.

Key Points

• Chronic hyperglycemia damages nerve fibers through multiple mechanisms, including oxidative stress, formation of advanced glycation end products, and microvascular damage that reduces blood flow to nerves 1.
• This affects both sympathetic and parasympathetic branches of the autonomic nervous system, leading to dysfunction in multiple organ systems, including cardiovascular, gastrointestinal, genitourinary, and sudomotor systems 1.
• Patients may experience cardiovascular issues (resting tachycardia, orthostatic hypotension), gastrointestinal problems (gastroparesis, diarrhea, constipation), genitourinary dysfunction (erectile dysfunction, neurogenic bladder), sudomotor dysfunction (anhidrosis), and impaired pupillary responses 1.
• Maintaining blood glucose levels within target ranges (typically fasting 80-130 mg/dL and postprandial <180 mg/dL) through medication adherence, regular monitoring, proper diet, and exercise is essential to prevent or slow progression of autonomic neuropathy 1.
• Once established, autonomic neuropathy is difficult to reverse, making prevention through tight glycemic control the most effective approach 1.
• Individuals with diabetic autonomic neuropathy should undergo cardiac investigation before beginning physical activity more intense than that to which they are accustomed 1.

Prevention and Management

• Tight glycemic control is the most effective approach to prevent or slow progression of autonomic neuropathy 1.
• Regular monitoring and proper diet and exercise are also essential in preventing or slowing progression of autonomic neuropathy 1.
• Cardiac investigation is recommended before beginning physical activity more intense than that to which they are accustomed in individuals with diabetic autonomic neuropathy 1.

From the Research

Effects of Poor Glycemic Control on the Autonomic Nervous System

• Poor glycemic control can lead to autonomic neuropathy, a complication of diabetes that affects the autonomic nervous system, which innervates the entire human body and regulates every single organ 2.
• Autonomic neuropathy can result in various abnormalities, including resting tachycardia, postural hypotension, orthostatic bradycardia, and orthostatic tachycardia, as well as exercise intolerance and decreased hypoxia-induced respiratory drive 2, 3.
• The risk of cardiac autonomic neuropathy (CAN) is increased with poor glycemic control, and CAN is associated with a five-fold increased risk of cardiovascular mortality 3.
• Poor glycemic control can also lead to an imbalance between the sympathetic and parasympathetic nerve fibers, resulting in abnormalities in heart rate control and vascular dynamics 2.

Risk Factors for Autonomic Neuropathy

• Poor glycemic control is a significant risk factor for autonomic neuropathy, particularly in type 1 diabetes 4, 5.
• Other risk factors for autonomic neuropathy include diabetes duration, hypertension, dyslipidemia, and obesity 3, 5.
• The presence of aldose reductase gene (AKR1B1) polymorphisms, specifically the Z-2/Z-2 genotype, is also a risk factor for autonomic neuropathy in young people with type 1 diabetes 5.

Diagnosis and Treatment of Autonomic Neuropathy

• Diagnosis of autonomic neuropathy can be made using various methods, including assessment of symptoms and signs, cardiovascular reflex tests, and short-term electrocardiography (ECG) 3.
• Treatment of autonomic neuropathy is based on early diagnosis, lifestyle changes, optimization of glycemic control, and management of cardiovascular risk factors 3.
• Pathogenetic treatment of autonomic neuropathy includes balanced diet and physical activity, optimization of glycemic control, treatment of dyslipidemia, and antioxidants such as α-lipoic acid (ALA) 3.