Scientists do not know the exact cause of proximal neuropathy. Poorly controlled glucose (blood sugar) is known to be a contributing factor in development of all forms of diabetic neuropathy. High glucose (hyperglycemia) appears to have a chemical reaction with the nerves or cells around the nerves. This reaction damages the nerves, causing poor transmission of signals between the body parts and the brain.

Uncontrolled glucose can also directly damage the blood vessels (diabetic angiopathy). The resulting poor circulation has also been linked to neuropathy. The blood vessels carry oxygen and nutrients to the nerves, which keeps them healthy. Without proper blood flow, the nerves do not receive these elements from the blood and can die. An active lifestyle helps promote a healthy heart and good circulation. Proximal neuropathy occurs more frequently in older individuals who are not always able to remain active.

Smoking and alcohol use are associated with all diabetic neuropathies. Though modest use of alcohol has been found to have some health benefits, it is a nerve toxin, causing harm to the nerves in the body. Smoking causes damage by:

• Lowering the amount of oxygen that reaches tissues
• Constricting the blood vessels
• Increasing blood pressure
• Raising glucose levels

Although poorly controlled glucose is linked to neuropathy, proximal neuropathy often appears in people with diabetes with only mildly elevated glucose levels. In addition, significant unexplained weight loss commonly occurs with proximal neuropathy. Researches are not sure how these two factors contribute to the development of the condition. It is clear, though, that most people with diabetes with proximal neuropathy have difficulties controlling their glucose, regardless of the level.